PROGRESS REPORT 1983 -1984 Instituto De Física Universidade Federal Do Rio Grande Do Sul

PROGRESS REPORT 1983 -1984 Instituto de Física Universidade Federal do Rio Grande do Sul

Ptrtt 1MS FOREWORD

During the last two years, period covered by the present Progress Report, the economical situation of the country has become very bad. Since the University is not an isolated structure, this situation has affected our academic life as a shortage of financial support for research and as a general lack of resources, not only material but also human. In this framework, for nearly three months, starting May 1984, the staff of all the Federal Universities of the country went on strike for better salaries and more investment in education. In our particular case, for three months we have stopped with all teaching and almost all research activities. Despite these difficulties, our research activities have been very productive, as can be observed by looking through the present Progress Report. The main exception is the area of Perturbed Angular Correlation, which has been showing a steady decrease in activity during the last four years. This is a consequence of the fact that most of the senior physicists who worked in this area have shifted their scientific interest to other fields of research. One such field is Ion Implantation, which during 1983-1984 has been definitively established as a research area of the Institute. A 400 keV Ion Implanter has been operating since the end of 1982 at the new Campus of the University. The new group associated to this machine, starting basically from scratch, has progressed rapidly as can be deduced from the papers published in international journals, active participation at International Meetings and a fruitful interchange with other national institutions and with groups from foreign countries. As a consequence of the growing financial difficulties we have been forced to reduce drastically the importation of all kinds of equipments and spare parts. In order to fulfill our needs, a growing activity of local developments in instrumentation has been observed. This activity is reflected in the Technical Section of the present Progress Report, which has increased significantly as compared with the last one. The scientific achievements of the Institute of Physics ' were possible due to the financial support of Financiadora de Estudos e Projetos (FINEP), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES). The continuous support received from the University administration is also acknowledged. The dedication of our technical and administrative staff and the enthusiasm of the graduate students were also essential factors in the reported scientific achievements. Finally the effort of Dr. Moni Behar in editing this volume and the hard work of Mrs. Ivone H. Schunck in typing it are gratefuly acknowledged.

Edemundo da Rocha Vieira, Director, Institute of Physics TABLE OF CONTENTS Page I. EXPERIMENTAL PHYSICS I.a) Perturbed Angular Correlation and High Pressure Studies -Interferometric High Pressure Gauge for the Diamond Anvil Cell Useful at High Temperatures 2 / -Phase Transition and Compression of LiNbO, Under Static Very High Pressure 2 / -The Temperature Dependence of the Electric Field Gradient in , InSe Switching Compound 3 '/ -Anomalous Temperature Behaviour of the Electric Field Gradients ,,' in an InSe Semiconductor Compound 3 -Structural Changes in the Switching InSe Compound Studied by the TDPAC Technique 3 '••/ I.b) MBssbauer Spectroscopy -Magnetic Anisotropy Study in the Intermetallic Compounds ErFe-H and (Er Gd )Fe, by 57Fe MBssbauer Spectroscopy '} / J X I ™X X J l/ - Fe MtJssbauer Study of the Magnetic Properties of (Fe,Mn)WO4 3 -MBssbauer Effect in a Sample of Ferroaugite-Ferrohedenbergit 6 -Hyperfine Fields at sp Sites in Heusler Alloys Rh.MnZ (Z « Ge, Sn, Pb) b ^ -Magnetic Properties of the Hydride Pd3FeHQ ? 7 ^ -Hyperfine Magnetic Fields in (Pd,Au)_Fe 7 y I.c) Ion Implantation -Intennetallic Phases Formed During Tin Implantation into Iron and Steels / -Comparative Study of Intermetallic Phases Formed by Direct Ion Implantation and Radiation Enhanced Diffusion of Tin in Two , Kiud3 of Steel 9 / -Radiation Enhanced Diffusion 10 -Energy Dependence of the Z.-Range Oscillation Effect in Amorphous Silicon 10 ^ -Analysis of RBS Spectra with Low Mass Resolution 11'/ -Distribution of Light Ions and Foil Destruction after Irradiation of Organic Polymers 12v -Range Profiles of 10 to 380 keV 120Sn and 133Cs in Amorphous Silicon 13^ -The Suppression of Residual Defects in Silicon Implanted with , Arsenic by Rapid Isothermal Annealing 14 / -langt Profiles of Implanted Bi and Au in Amorphous Silicon 15 / Page

-Implantation and Thermal Annealing Behaviour of Bi Implanted into Al/Ti Bilayer Structure 15 '/ -Implantation and Thermal Annealing Behaviour of Bi Implanted into A1/KC1 Bilayer Compound 16 ' 69 -Range and Range Straggling of 15 to 350 keV Ga in Amorphous i Silicon 17" -Adhesion Enhancement Induced by MeV Ion Beams 18 ' -High Sensitivity Carbon Content Analysis of Geological Materials Using 1,4 MeV Deuterons 18 • -Heavy Ion Rutherford Scattering for Measurement of Heavy Element Concentrations and Isotopic Ratios 19 ' -Electrical Contact and Adhesion Modification Produced by High J Energy Heavy Ion Bombardment of Au Films on GaAs 20 . V -Two Types of MeV Ion Beam Enhanced Adhesion for Au Films on SiO- 20 -Ion Implantation Metallurgy 21 '•/ -Recoil Implantation of Antimony into Silicon by Argon Ion Bombardment 22 / I.d) Electronic Transport and Magnetism

-Properties of the Pure Heusler Phase of the Cu7MnSn Alloy 23 V -Magnetoelastic Properties of ErFe- 23 / -Macroscopic and Microscopic Magnetism of Amorphous Metal-Metalloid Alloys 24

-Results and Ideas of Electronic Transport in Amorphous Metals 24 J -The Role of Zr in Electronic Transport of Amorphous CuZr 25

-Order-Disorder Transition in NiMn Alloys 25 '•/ -Magnetic Properties of Mixed System Pt.(Mn,Fe) 26

1 -Electrical Resistivity of the Pt_(Mn,Fe) and the

(Pt,Pd)3Fet Alloys 2b / -Electrical Resistivity of the Co.VAl Heusler Alloy 26 / -Crystallization of Amorphous Pseudobinary Alloys Type 27 l/ -Magnetostriction of Pd-Fe Alloys 27 / -Activation Energies for Crystallization of Amorphous Metals 28 V -Electrical Resistivity of the Ni-Mnln Heusler Alloy 28 \

-Spin-Disorder Resistivity in the Ni9Mn(Sn. In ) Heusler Alloys 29 • / » I ^X X -The Effects of the Chemical Order-Disorder on the Magnetic 29 Anisotropy of NiMn Spin Glasses / -Spin-Glass Behavior as a Function of Concentration and Local Order by NMR in Nearly Random NiMn Systems 30 -Extended and Local Effects of Cold Work in Heusler Alloys 30 v/ Page -NMR and Magnetization Study of the Mixed Syst< (Pd Cu ).MnIn and (Pd^ Ni^jMnln 31 ' -Magnetoresistance of Pd-Fe and Pd-Ni-Fe Alloys 31 u I.e) Laser -Birefringence in Optical Coatings 32 " -Fora Birefringence in Thin Films 32 -Computer Simulation of Thin Film Growth: Applying the Results , to Optical Coatings 33 ' -Deposition, Characterization, and Simulation of Thin Films with Form Birefringence 34 * -A Grazing Incidence Dye Laser with an Intracavity Lens 35 V -Extended Linear Tuning of a Dye Laser with Intracavity / Fabry-Perot and Diffraction Grating 36 * -Atlas of the B-X Absorption Transition of Molecular Iodine 36 * -Feco-Based Observation of Birefringence at Normal Incidence in Optical Coatings 37 / -Measurement of the Principal Refractive Indices of Thin Films / Deposited at Oblique Incidence 37 ^ -Determinaiiou of Principal Refractive Indices of Birefringence / Thin Films 38 ' I.f) Intermetallics -Inductive Observation of Transitions from [100] Magnetic Domains to [010] and [001] in Silicon-Iron 40 •y -Remarks on Alloying-Induced Lattice Parameter Changes in Internetallie Compounds 40 -A Model for the E.Q.I, in High d-Density of States Metallic Systems 41 / T T Fe -A Model for the Electronic Structure of ( i_x x) 2 Intermetallic Compounds: An Application to (Zr Hf )Fe_ 41 t/ -Mbssbauer Study of Pseudobinary Ur Hf )Fe~ Compounds 42 /'

II. THEORETICAL PHYSICS 11.a) Nuclear Physics -Lifetime of a Nuclear Hole State in a Field-Theoretic Model 44 *' -Bags in the Shell Model 44 / -Effective Polarization in Quasi-Free Scattering and Nuclear Structure 45 ^ -Recent Developments in Quasi-Free Mucleon-Nucleon Scattering 45 '/ -Mean Free Nucleon Path in Nuclear Matter 46 / -KN Scattering in the Cloudy Bag Model: s, p and d-Waves 46 1/ Page

-S-Wave Meson Nucleon Scattering in an SU(3) Cloudy Bag Model 47 V

-Kaon-Nucleon Scattering in an Extended Cloudy Bag Model 47 •/ -Pion-Nucleon Scatterings Lengths in the Cloudy Bag Model 48 V — 13 12 48 V -Excitation of Low-Spin (AN) States in C(p,d) C* 49 / -Multiple A(1236)-Rescattering in Nuclear Pion Absorption 49

-A-Isobar Effects in Quasi-Free Scattering •/ 50 -Quark-Meson and Barion-Meson Couplings -Long and Intermediate Range Baryon-Baryon Interaction in the 50 l/ Chiral Bag Model -Relativistic Mean-Field Formulation for Baryonic Systems 51 12 • I -E-Hypernuclear Low-Lying States in C 51 Li -Simplified Relativistic Formulation of Short-Range Correlations for Baryonic Interactions 52 /

-Center-of-Mass and Recoil Corrections in Bag Models 52

-Quantization of QED and QCD in a Fully Fixed Temporal Gauge 53 / -Operator Quantization of Non Abelian Gauge Theories in a Completely Fixed Axial Gauge 54 V -Dynamics of Gauge Systems and Dirac's Conjecture 54 II.c) Solid State -Effect of the d-f Coulomb Correlation on the Valence Transition of Intermediate Valence Systems 55 -Real Space Renormalization of an Anderson Impurity in a Linear Chain 55 -Electronic Transport in Amorphous Metals 55 V -Contribution of the Torsional Modes to the Equilibrium Distribution of Vibrational States and to the Specific Htat of a Chain Molecule 56 1/ -Renormalization and Critical Behavior of the Continuous Potts Model with External Symmetry Breaking 57 '/ -Effects of Trilinear Symmetry Breaking on the Potts Model Transition of Uniaxially Stressed SrTiO. 57 / -Real Space Renormalization Group and Electron Localization in Random Potentials 58 -Quantum Spin Glass. A Replica Symmetric Theory with Positive Entropy 58 -Second-Quantized Theory of Anderson Localization in d • 2+c 59 i/ Page

-Singularities in the Paramagnetism of Two-Dimensional Nearly Magnetic Itinerant-Fermion Systems at very low Temperature: / Application to Degenerate Two-Dimensional Liquid-^He Films 60 -Quantum Ising Spin-Glass 61 * -Critical Exponents for $ -Field Models with Long-Range /- . Interactions 61 v -Crossover from First-Order and Near-Spinodal First-Order to / Continuous Transitions in the Three- and Four-State Potts Model 62 * -Validity of the Long-Range Expansion in the n-Vector Model 62

-Crossover Exponents for the Potts Model with Quadratic Symmetry / Breaking 63 V -First-Order Phase Transitions in the Potts Model with Trilinear / Sy^n«rrv breaking 63 ' -Effect of the Coulomb Repulsion Between Localized and Itinerant / Electrons in the Anderson Hamiltonian 64 / -The Liquid Metal Models Applied to Glassy Metals 65 ^ -Kondo-Type Theories Applied to Amorphous Metals 65 ]/ -Metallic Glass Formation 66 -A New Approximation for the RFK Model 66 / -Effect of the Spatial Correlation on the Alloy Analogy , Solution of the Hubbard Hamiltonian 66 ^ -A Diagrammatic Method for a Mixed Valence Hamiltonian 67 • -Effect of d-f Correlation on the Electronic Structure of Intermediate Valence Systems 67 u y -Green-Function Method for a Mixed-Valence Hamiltonian 68 -Binding Energy of a Hydrogen Impurity in an f.c.c. Lattice 68 -Real Space Renormalization of a Mixed Valence Hamiltonian II.d) Plasmon a Betha e Lattice 68// -Wave Absorption by Fast Electrons with Non-Maxwe11ian Perpendicular Momentum Distributions 70 -Effect of Electron Thermal Anisotropy on the Kinetic Cross-Field Streaming Instability 70 -Excitation of Whistler Waves by Reflected Auroral Electrons 71 -Momentum Distribution Dependence of Induced Electron-Cyclotron Emission 71 -Angular and Momentum Distribution Dependence of Electron Cyclotron Absorption and Amplification in Mirror-Confined Plasaas 72 -Instabilities Excited by an Energetic Ion Beam and Electronic Temperature Anisotropy in Tandem Mirrors 72 Page

-Instabilities Due to Transmitted and Reflected Ions and Electron Temperature Anisotropy in a Quasiperpendicular Shock Wave 73

-Induced Electron-Cyclotron Emission from Inhomogeneous ( Anisotropic Plasmas with Electron Population Inversion ' 74 -Dissipative Instabilities in the Edge of Reversed-Field Pinches Driven by a Combination of Plasma Gradients and a Parallel Current 74 -Exact Solutions of the Time-Dependent Vlasov Equations ; 75^ -Thermal Instabilities in the Edge Region of Reversed-Field Pinches 75 -The Effect of Thermal Processes on Stability in the Edge of Reversed-Field Pinches 76 -Exact Invariants in the Form of Momentum Resonances for Particle Motion in One-Dimensional, Time-Dependent Potentials 77

III. ASTRONOMY AND ASTROPHYSICS -Spectrophotometry of the Nucleus of NGC 7552 79 -Age Determination of HII Regions of the LMC and SMC 79 -Burst of Star Formation in Detached Extragalactic KII Regions: A Qualitative Analysis 79 -A Study about the Existence of Periodic Components in the U, B, V Variability of Seyfert Nuclei 80 -The 1051 s Period of the Interacting Binary White Dwarf AM CVn 88 -The ZZ Ceti Star GD 385 Revisited 88 -The Distribution of Interstellar Extinction Near the Sun 89 -BV Surface Photometry of the Southern Galaxies NGC2855 and NGC4507 89 -B, V, and DDO Photometric Observations of Red Variable Stars 93 -Light and Line Profile Variations due to r-Mode Pulsations . , with an Application to the ZZ Ceti Star G117-B15A 93 -BV Surface Photometry of the Galaxies NGC6769, 6770, 6771 94 -Age Determination of HII Regions of the LMC and SMC 95 -Age Determination of Galactic and Extragalactic HII Regions 96 -HII Regions Age Indicators 97 -DDO Integrated Photometry of Globular Clusters and Initial Chemical Evolution of the Galaxy 97 -DDO Photometry and Metallic Abundances of E and SO Galaxies and Globular Clusters of the LMC and SMC 98 -DDO Photometry on Red Giants in the Open Clusters NGC 2232, NGC 2287, and NGC 2451 98 -PG 1116+158 99 Page

-Relationships of a Growing Magnetic Flux Region to Flaves 99 -Ephemeral Regions vs. Pseudo Ephemeral Regions 100

IV. PHYSICS EDUCATION -Laboratory Teaching Materials for Secondary Schools 103 -Experimental Physics Teaching in Secondary Schools: An Attempt to Make it Feasible 104 -Equipment for Secondary Schools - Teacher's Guide - Vol. II - Electricity 105 -Equipment for Secondary Schools - Teacher's Guide - Vol. Ill - Optics 105 -Concept Maps as Instruments for Learning Evaluation 105 -Concept Maps as Tools to Investigate Cognitive Structure in Physics 106 -Experimental Activities to the Teaching of Fluid Mechanics at Introductory College Level 106 -Entrance Examination: Comparison of Students Achievement in Four Areas of Physics 106 -Discrimination Index of Psychometric Tests Items Correction 107 -University Teaching: Texts Concerning Basic Components of Instructions 107 -Assessment of Content and Cognitive Structure in Physics at College Level 108 -A Cognitive Approach to Physics Teaching 108 -Different Approaches to Laboratory Teaching 109 -Student Evaluation of Teacher's Performance: Evidences of Validity of an Instrument 109 -Improving University Teaching: Supporting Small Projects as a Strategy for Instructional Development 110 -Measuring Attitude Towards the Laboratory in Introductory College Physics 110 -Teaching and Learning: Theoretical Approaches 110 -The Use of Concept Maps in the Analysis of Curriculum 111 -Double Evaluation of Essays: Comparing Scores 111 -Concept Maps as Instructional Tools in Physics Teaching 112 -Analyses of Items of the Entrance Examination of the UFRGS-1984 112 -Cognitive Mapping in Thermodynamics Through Multidimensional Scaling 113 -Inference about the Mean Using a Set of Data: an Aspect Related to the Sensitivity of Measurement 113 -Considerations on the Discrimination Index of Itens in Educational Tests 114 Page

-The Content Analysis as a Tool of Evaluating Learning in Physics

V. INSTRUMENTATION -Reliable Room Temperature Compensation for Thermocouples 117 -Simple D.C. Differential Resistometry for Long Term Experiments 117 -AC Susceptometer for Measurements in the 4 to 300 K Temperature Range 118 -Superisolated Dewars 119 -Low Temperature Implantation Chamber 119 -Data Acquisition System for Susceptibility and Resistivity Measurements 120 -Temperature Measurements Using Resistance Thermometers at Low Temperatures 120 -Proportional Temperature Control for Resistance Furnace 121 -Low Frequency AC Differential Resistance Detection 122 -A Microcomputer Data Acquisition System for Pulsed Dye Laser Spectroscopy Experiments 123 -Magnetoanisotropies in Fe-Si Foils and its Utilization in Force Transducers 124 -Design and Construction of Precision Translators 124

VI. APPENDIX

-Papers Published 126 -Papers Accepted for Publication 135 -Papers Presented at Meetings and Conferences 139 -M.Sc. Theses 155 -Ph.D. Theses 156 -Staff Members of the Department of Physics 158 -Staff Members of the Department of Astronomy 160 -Engineering Staff of the Institute of Physics 160 -Graduate Students of the Institute of Physics: -Ph.D. Students 161 -M.Sc. Students 162 RESEARCH IN THE FIELD OF EXPERIMENTAL PHYSICS -2-

Interferometric High Pressure Gauge for the Diamond Anvil Cell Useful at High Temperatures* + t t J.A.H. da Jornada , S. Block and G.J. Piermarini

A new method of precise pressure measurement in the diamond anvil cell, especially useful at high temperatures, is presented. It is based on the measurement of the chanelled spectrum of a miniature Fabry-Perot etalon interferometer placed inside the cell. The validity of the methru has been verified with an interferometric gauge of ZnWO,.

*Appl. Phys. Lett. £5(6) 1984. •On leave from IF-UFRGS, Brazil. tCenter for Materials Science, National Bureau of Standards, Washington D.C. 20234

Phase Transition and Compression of LiNbO Under Static Very High Pressure*

J.A.H. da Jornada"1", S. Block , F.A. Mauer and G.J. Piermarini'

Lattice parameters of LiNbO- were measured at room temperature over the pressure range from 0 to 35 GPa by X-ray diffraction using the diamond anvil cell. In the region below 13 GPa (where a hydrostatic pressure was maintained) the pressure dependence of the volume can be well described by the Birch- Murnaghan equation of state, yielding B = 134±3 GPa for the zero pressure bulk modulus and B1 = 2.9 + 0.5 for its pressure derivative. A phase transformation was detected at 30+3 GPa both by X-ray diffraction and by optical observation of the change from a transparent to an opaque state. The pattern of the high pressure phase was tentatively indexed on the basis of a cubic cell with a - 6.78 A*.

^Accepted for publication in Journal of Applied Physics. +0n leave from IF-UFRGS, Brazil. tCenter for Materials Science, National Bureau of Standards, Washington D.C. 20234. -3-

The Temperature Dependence of the Electric Field Gradient in InSe Switching Compound

M. Behar, E.R. Fraga, A. Maciel, W. Schreiner and H. Saitovitch*

Measurements of the time perturbed angular correlation of the well known 173-247 kcV In gamma-gamma cascade in InSe show very remarkable features. When InSe is switched to the on-state (low resistivity) it presents one frequency whose temperature dependence is linear from 4 K to room temperature. When InSe is in the off-state (high resistivity) it shows two other quadrupole frequencies, being one almost constant with the temperature while the 3/2 other follows a linear temperature dependence from 4 K to 80 K and T behaviour above this temperature. These tacts strongly indicate a change in the structure when the InSe switches from the off-state to the on-state, which may be associated to the formation of conducting filaments between the layers. *Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro, RJ, Brazil.

Anomalous Temperature Behaviour of the Electric Field Gradients in an InSe Semiconductor Compounds*

L. Amaral, M. Behar, A. Maciel and H. Saitovitch

The temperature dependence of the nuclear quadrupole frequencies acting at two sites of indium in an InSe semiconductor compound was measured between 4 and 823 tC, using the TDPAC technique. One of the frequencies remains constant through the whole temperature range. The other, instead, follows a 3/2 linear dependence up to 80 K and then the well-known T relationship.

*Physics Letters 102A (1984) 45. •Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro, RJ, Brazil.

Structural Changes in the Switching InSe Compound Studied by the TDPAC Technique*

L. Amaral, M. Behar, A. Maciel, L.S. de Oliviera and W.H. Schreiner

By using the TDPAC technique we were able to detect and follow the structural changes suffered by the compound InSe when submitted to a switching process. For these changes well defined electric quadrupolar -4-

frequencies, Which appear and/or disappear, are associated, as clearly observed in the experimental results.

*J. Phys. C: Solid State Phys. J£ (1983) LI039. -5-

Magnetic Anisotropy Study in the Intennetallic Compounds ErFe^H

and (Er1_xGdx)Fe3 by Fe Mflssbauer Spectroscopy**

J.B.M. da Cunha, P.J. Viccaro and A. Vasquez

The magnetic anisotropy in the ternary hydrides ErFe.H and in the 57X pseudobinary (Er Gd )Fe compounds has been studied by Fe MHssbauer 1 *X X j spectroscopy. ErFe. shows a spin reorientation from basal plane above 47 K to the C axis below this temperature. The direction of the magnetization is the result of a competition between the crystal field anisotropy at the Er sites, the magnetic exchange interaction and the iron sub-lattice anisotropy. The results show that this spin reorientation in the hydride at 240 ± 5 K is independent of the hydrogen concentration. For the pseudobinary (Er Gd )Fe.. I *™X X y a decrease in the reorientation temperature is observed as the Gd concentration increases. Above 20 at% Gd, no reorientation occurs. For the hydride, the results are consistent with changes induced in the crystal field anisotropy and magnetic exchange interaction induced by the presence of hydrogen. The decrease in the reorientation temperature with the Gd concentration can be described by a single particle model in which the free energy is calculated in terms of the magnetic exchange and relevant crystalline electric field interactions.

*Hyp. Int. 15/16 (1983) 697-700 and to appear in J. of Physics F. +Work supported in part by CNPq and FINEP, Brazil.

Fe MBssbauer Study of the Magnetic Properties of (Fe,Mn)W0,

W.A. Mundt, A. Vasquez and P.J. Viccaro

Both the mineral Feberite (FeWO,) and Huebnerite (MnWO,) are antiferromagnetic below 14 K and 76 K, respectively. However, the magnetic spin structure and easy axis are different in the two cases. We have studied the mixed system (Fe,Mn)W0, over the entire concentration interval using Fe MBssbauer spectroscopy. Our results show that for concentration of Fe on the order of 0.5 atZ, the spin structure of MnWO, changes to one similar FeWO,. 57 HI* The Fe hyperfine parameters indicate that a rotation of easy axes of the system occurs at this concentration. In order to interpret these data, we -6-

have developed the crystal field Hamiltonian appropriate for Fe in the structure, using the point charge approximation and Stevens operators. Lattice sums were made to determine the coefficients A of the expansion. The electronic structure and all pertinent single ion properties of Fe in the structure have been determined from the Hamiltonian and will be compared to those obtained from the Mtlssbauer data. From this analysis, we expect to obtain information concerning the exchange interactions and single ion anisotropies responsible for the magnetic behavior in this mixed magnetic system.

MBssbauer Effect in a Sample of Ferroaugite-Ferrohedenbergite

J.I. Kunrath, E. Frank* and C.S. Mill ler

The Fe Mtissbauer spectra of Ferro-augite and hedenbergite in the temperature interval of 4.2 -*• 1100 K show the existence of three iron sites. In one of these sites, an unusual temperature variation of the quadrupole splitting is observed. This variation can be accounted for using a distortion isomerism of the immediate distorted octahedral environment, with an activation energy of 1200 cal/mol. In addition, it is found that at 9.8 K a magnetic transition occurs. The saturated hyperfine magnetic field is found to be approximately 142 kOe at 4.2 K.

^Present address: Química Hoechst S.A., Division Tensioactivos, Corrientes 222, Buenos Aires, Argentina.

Hyperfine Fields at sp Sites in Heusler Alloys Rh-MnZÍZ-Ge, "n, Pb)

S.M.M. Ramos, A. Vasquez, J.B.M. da Cunha, S. Jha*, H.M. Seyoum*, G.M. Julian** and R.A. Dunlap*

119 The MBssbauer effect has been used to study the Sn magnetic hyperfine fields (H ) in the Heusler alloys Rh.MnZ Sn , where Z is a sp element n i. U.7n QQO nu.u nn z (Z • Ge, Pb, Sn). The results in these alloys are compared with those for the

Heusler alloys X2MnZ (X - Co, Ni, Cu, Pd). The H were analysed in terms of the conduction electron polarization -7-

density at the Z site and its dependence on the distance from the Mn atom. Although we can't describe quantitatively the H results with the well-known models for induced K in sp elements, our results show that the H systematic

in Rh_MnZn ooSn_ no are more similar to that for Co-MnZ alloys, in which Co carries a magnetic moment, than to the X_MnZ alloys with X = Ni, Cu, Pd which carry no magnetic moment.

*Physics Department, University of Cincinnati, Cincinnati, Ohio, 452?1, USA. **Physics Department, Miami University, Oxford, Ohio 45056, USA. +Physics Department, Dalhousie University, Halifax, Nova Scotia B3H 3J5, C&n.

*+ Magnetic Properties of the Hydride Pd-FeH-

M.H. Preis Corrêa, W.H. Schreiner, J.E. Schmidt, P.J. Viccaro and A. Vasquez

Results of magnetization and Fe Mtissbauer measurements show that the strong ferromagnetic coupling in Pd_Fe is markedly altered in the hydride

Pd-FeH0 7. The magnetic moment of (4.59 ± 0.03)vi is reduced by the presence

of hydrogen to (0.83 ± 0.03)uD. This reduction is accompanied by a decrease of approximately 46Z in the magnetic transition temperature of the hydride compared to that of Pd-Fe (499 K). In addition MBssbauer spectra at 4.2 K in external magnetic fields indicate that anisotropic antiferromagnetic coupling dominates in the hydride. Results are compared to those for Pd«AuFe where similar effects are observed.

*To appear in Journal of Physics F. •Work partially supported by CNPq and F1NEP (Brazil).

Hyperfine Magnetic Fields in (Pd,Au)_Fe*+

Rejane M. Ribeiro-Teixeira, M.H. Preis Corrêa, A. Vasquez and C.E.T. Gonçalves ca Silva*

We present here a self-consistent model calculation of the magnetic moment and average electron occupation of the d-band in the Fe sites in (Pd Au ).Fe alloys. These are compared with MBssbuaer results for the -3-

hyperfine fields measured at the iron atoms in the ternary alloys. There is a reasonable agreement of the theoretical results with the experimental ones. A decrease was observed for the field at the Fe nucleus in (Pd Au ),Fe with increasing Au concentration. The results obtained confirm the idea that at least part of the reduction of the hyperfine field in hydrogenated ordered Pd-Fe is due to the loss of Pd momentum upon H uptake.

*Physica 124B (1984) 218. +Work supported in part by CNPq and F1NEP. §Institute» de Física Gleb Wathagin, UNICAMP, 13100 Campinas, SP, Brazil. -9-

Intermetallic Phases Formed During Tin Implantation into Iron and Steels**

P.H. Dionisio, B.A.S. de Barros Jr. and I.J.R. Baumvol

The surface layers of pure iron, high-carbon steel and stainless steel, ion implanted with 1x10 Sn -cm" , have been characterized by means of Sn conversion electrons Mtissbauer scattering. The intermetallic phases existent in the as-implanted samples are determined, and then the thermal decomposition of these phases are established. The phase transformations observed in the treated surfaces agree reasonably well with the phase diagrams reported in the literature for stoichiometric intermetallic phases formed in bulk.

*J. Appl. Phys. 55(12) (1984) 4219. +WV>rk supported in part by FINEP, CAPES and CNPq (Brazil).

Comparative Study of Intermetallic Phases Formed by Direct Ion Implantation and Radiation Enhanced Diffusion of Tin in Two Kinds of Steel**

P.H. Dionisio, B.A.S. de Barros Jr. and I.J.R. Baumvol

The surface layers of high-carbon and stainless steel samples, treated by both direct ion implantation of Sn ions and radiation enhanced diffusion of tin, are analysed by means of Rutherford backscattering and Sn and Fe conversion electron Mtíssbauer spectroscopy. The intermetallic phases formed in the treated surfaces are determined, and their thermal evolution is established. The compositions and phase transformations observed in the surface of the samples treated by both direct ion implantation and radiation enhanced diffusion are very similar, and this similarity indicates that these two treatment processes are essentially equivalent for practical applications.

*To be published in The Journal of Applied Physics. •Work supported in part by FINEP, CAPES and CNPq (Brazil). -10-

Radiation Enhanced Diffusion

C. Scherer, P.C. D'Ajello and L. Lauck

The study of the dynamics of Radiation Enhanced Diffusion in a solid involves a sequence of problems to be solved before we have a complete theoretical understanding of the process. The energy deposition of the incident particles in the sample, the creation of deffects (mainly vacancies and intersticials), the diffusion of these deffects, the modification of the diffusion coefficient for the impurity, which become a function of position and the solution of the diffusion equation appropriate for this inhomogeneous medium. We have started our study by assuming that the source of deffects is known. Assuming also that the diffusion of the deffects is a rapid process, so that a stationary distribution is achieved in a time much shorter than the characteristic time of the diffusion experiment, our first task is to obtain this stationary distribution from the system of diffusion equations for the deffects. This system is non-linear due to the recombination of vacancies and intersticials. We developed a numerical algorithm to solve it with appropriate boundary conditions. Bases on a random walk model we then calculate the diffusion coefficient for the impurity as a function of the concentrations of deffects. The final task of solving the diffusion equation is also done numerically. Once we have control of the whole process it is an easy task to play with the various physical parameters involved and, by comparing the results with experimental data we can learn about the physical properties of the sample. We have obtained numerical results for several examples of parameter values, which, together with the details of the model, will be submitted for publication in "Radiation Effects",

Energy Dependence of the Z -Range Oscillation Effect in Amorphous Silicon

M. Behar, J.P. Biersack*, P.F.P. Fichtner, D. Fink*, C.A. Olivieri, J.P. de Souza and F.C. Zawislak

79 85 Projected ranges (R ) and projected range stragglings (AR ) cf Br, Kb, 108 174 ^ ^ Pd and Yb implanted at various energies from 10 to 380 keV in amorphized silicon wafers, are compared with recent universal range-energy calculations. -11-

Very gocd agreement is obtained between experimental and calculated (Monte Carlo code TRIM) values of R and AR for Br and Pd in all the measured energy P P range. The low energy data (up to 50 keV) for Pb and Yb show calculated values of R lover than the experimental values. These data, together with our P earlier results for the pairs Au-Bi and Sn-Cs are analysed in terms of the Z.- range oscillation effect.

*Hahn-Meitner-Institut für Kernforschung Berlin, Glienicker Str. 100, D-1000 Berlin 39, West Germany.

Analysis of RBS Spectra with Low Mass Resolution

C. Scherer, S. Teixeira and I.J.R. Baumvol

When one observes the spacial distribution of some ".mpurity close to the surface of a solid, using Rutherford bsckscattering (RBS), if the atomic mass difference between impurity and host atoms is not large enough for the energy of the recoiling alpha particles, scattered by the impurity, to fall in a region of the RBS spectrum well separated from the region of alphas scattered by host atoms, the usual procedure of extracting the impurity concentration may not work. An example is shown in the figure, where the full line re- presents the RBS spectrum obtained with an alpha beam of 760 keV on a sample of Fe into which Sn has been introduced by radiation enhanced diffusion. The dotted line shows the corresponding spectrum of pure Fe. We have constructed an algorithm to separate the unresolved spectrum in two spectra, one for the alphas scattered by the host atoms, with atomic mass m. , and one for those scattered by the impurity atoms with atomic mass m. > m. . Starting from a channel for which the number of counts coincides with the case of pure host material (ex, E. in the figure) we calculate the position x. in the sample where the alpha particle, measured in this channel, has been scattered by a host atom. Calling E» the energy that the recoiling alpha should have if it had been scattered by an I impurity atom at x , we know that all -12-

counts in the channels between E. and E_ correspond to scattering by host atoms, since, for an impurity to scatter into these channels, it should be located deeper than x., where we know that the host material is pure. The difference between the measured spectrum and that of the pure sample represent in x-space lack of host atoms, which can be converted in volume concentration of the impurity between x. and x_, the position of the host atom which scatter into the channel with energy E_. Knowing this we can calculate how much of the counts in the channels between E_ and E. (see figure) correspond to alphas scattered by impurity atoms, which are in positions between x and x?. The difference between the total number of counts in these channels and the part corresponding to scattering by impurity atoms comes from host atoms. From these numbers we can calculate the density of host atoms in a new region of the sample, and so on. When we have analyzed the whole spectrum, if the concentration of impurity atoms is so high that the stopping power is considerably different from that of the pure sample, we recalculate it with the help of Bragg*s rule and repeat the calculation of the concentration by the same procedure just described. We repeat the whole procedure as many times as necessary to obtain a convergent result. This algorithm can be useful not only in our laboratory where the alpha beam is limited to a maximum energy of 760 keV, but also in laboratories with more powerful machines if the mass difference between host and impurity is too small to render a well resolved spectrum. The details of the calculation will be submitted for publication in Nucl. Inst. Meth.-B.

Distribution of Light Ions and Foil Destruction after Irradiation of Organic Polymers*

D. Fink*, J.P. Biersack*, J.T. Chen*, S. KlaumUnzer*, W. Schnabel*, M. StHdele**. K. Tjan**, M. Behar, C.A. Olivieri, F.C.Zawislak

It is found that light ions (Li, B) distribute neither according to their calculated range nor their nuclear damage distributions but according to their ionization distributions after implantation into organic polymers. Also, the profile of foil destruction after low dose light implantation (typically 12 14 10 -10 ions/cm1) obeys the ionization distribution rather than the range of nuclear damage distributions. After anneal respectively at higher implanted -13-

doses, a slight shift of the implantation or destruction profiles towards the damage distribution is found. The reason for this implantation behaviour may be partly understood in terms of diffusion and subsequent recombination with the created radicals. Li an4 B distributions in Carbon (which may be regarded as the final product of p.'lymer destruction) show a shape which can be described by range profiles with subsequent diffusion and trapping at homogeneously distributed defects. In contrast to the findings for light ijns in polymers, implanted heavy ions distribute essentially according to their range profiles, due to negligible diffusion after implantation.

*To be published in J. of Applied Physics. +Hahn-Meitner-Institut filr Kernforschung GmbH, Germany. ++Freie UniversitSt Berlin, Inst. f. Kernphysik, Germany.

120 133 Range Profiles of 10 to 380 keV Sn and Cs in Amorphous Silicon*

P.F.P. Fichtner, CA. Olivieri, J.P. de Souza, M. Behar, F.C. Zawislak, D. Fink+ and J.P. Biersack*

Depth profiles of Sn and Cs implanted at energies from 10 to 380 4 keV in amorphized silicon wafers are measured by He ion Rutherford backscattering. The obtained projected ranges (R ) and projected range stragglings (AR ) are compared with previous results and with recent universal range-energy calculations. The measured values of the profiles for Sn are in good agreement with the calculations. On the other hand, for Cs+ the situation is different. Our experimental R values are systematically lower than the predicted ones but the AR values are in quite well agreement. This difference is attributed to Z.-oscillation effect.

*To be published in Radiation Effects. +Hahn-Meitner-Institut fUr Kernforschung GmbH, Berlin, Germany. -14-

The Suppresion of Residual Defects in Silicon Implanted with Arsenic by Rapid Isothermal Annealing*

CM. Hasenack, J.P. de Souza and l.J.R. Baumvol

The shrinkage of device geometry, aiming higher packing density in integrated circuits, imposes the necessity of performing shallow doped regions with high control on the dopant profile. This control can be attained by using ion implantation to introduce the dopants into the substrate, but one has to minimize the profile redistribution during damage annealing. In order to overcome excessive spreading of the implantation profile which results from conventional furnace annealing and to provide high electrical activation yield combined with low residual defect density, several alternative energy sources have been explored. One of them is the infrared radiation emitted by a resistively heated sheet of graphite in the so called Rapid Isothermal Annealing (RIA) process. We have used Aligned Rutherford Backscattering to monitor the damage depth distribution level and the damage of silicon implanted with arsenic and submitted to RIA (Fig. 1). The RBS measurements were performed at the Porto 4 ++ Alegre HVEE-400 ion implanter using a He beam at 760 keV with a detector resolution of 14 keV. The alignment of the sample was done with a two axis goniometer designed by Joel Pereira de Souza. The results lead to the conclusion that an effective suppression

Figure 1

RBS spectra obtained from silicon samples implanted with arsenic; (a) <100> aligned spectrum for the sample as-implanted to a dose of 1x1016 cm"2; (b) and (c) random (upper curves) and <100> aligned (lower curves) spectra for the samples implanted with 1x10 As*cm and submitted to RIA at 1050 °C during 20 s (b) and 60 s (c); (d) the same as in (a) for o-, 1 n 16 implantatio: . n dose; (e) and OMNNB. NUMBER (f) the same as in (b)) and (c) for the 3x1016 cm"2 dose. -15-

of residula defects can only be obtained when the parameters of the anneal cycle employing RIA correspond to a redistribution of the implanted profile.

*Accepted for publication, NIM-B.

Range Profiles of Implanted Bi and Au in Amorphous Silicon*

P.F.P. Fichtner, CA. Olivieri, J.P. de Souza, M. Behar, F.C. Zavislak, D. Fink* and J.P. Biersack+

The Rutherford Backscattering technique is used to measure the depth 209 197 profiles for 10 to 390 KeV Bi and 15 to 390 keV Au implanted in amorphized silicon wafers. The obtained projected ranges (R ) and projected range stragglings are used to test the theoretical predictions from calculations using the new universal interatomic potential and screening length of Biersack and Ziegler. 209 Our measured values of the profiles for Bi are in good agreement with the theoretical predictions, while previous experimental data present system- 197 atical deviations at energies lower than 60 keV. On the other hand for Au our results have confirmed previous experimental values showing projected ranges higher than the predictions for energies up to 100 keV. The large difference (of about 50%) between the low energy ranges of ôi and Au is not reproduced by the existing calculations. One possible source of this dis- crepancy is the Z.-oscillation effect. Concerning the range stragglings, our experimental results are systematically higher than the calculations, but in agreement with most of the previously reported data.

*To be published in Nucl. Instr. and Methods B. +Hahn-Meitner-Institut fUr Kernforschung Berlin, Germany.

Implantation and Thermal Annealing Behaviour of Bi Implanted into Al/Ti Bilayer Structure*

C.A. Olivieri, M.Behar, P.F.P. Fichtner, F.C. Zawislak, D. Fink* and J.P. Biersack*

A bilayer sample formed by a 1500 % Al film evaporated onto a chemically cleaned Ti foil, was implanted with Bi** at an energy of 600 keV. The -16-

implanted depth distribution was analyzed using the Rutherford backscattering technique. The range profile of the as implanted sample clearly shows a concentration discontinuity at the interface region. This discontinuity as well as the whole range profile is very well reproduced by theoretical calculations using the Monte-Carlo TRIM simulation method . In order to study the thermal diffusion of the implanted ions, annealings for one hour at 200, 300, 400 and 500 °C were performed. At annealing temperatures between 200 and 400 °C only a small fraction of the implanted Bi becomes otobile, resulting in a near surface segregation and smoothing of the profile discontinuity at the Al/Ti interface. At 500 C an intermixing between Al and Ti occurs and as a consequence the Bi range profile suffers a drastic charge. Two main conclusions can be extracted from the present work. The first is that our results give further support to the theoretical assumptions used in the TRIM program, like the "new universal potential" and the improved electronic stopping power. The second is that the thermal behaviour of the implanted Bi cannot be reproduced by a regular thermal diffusion mechanism. It seems that most of the implanted Bi are trapped at the interface and are released only when intermixing between Al and Ti occurs.

*To be published in J. of Applied Physics. •Hahn-Meitner-Institut f(Jr Kernforschung Berlin, West Germany. 1) J.P.Biersack and L.G.Haggmark, Nucl. Inst. and Methods 174 (1980) 267.

Implantation and Thermal Annealing Behaviour of Bi Implanted into A1/KC1 Bilayer Compound

C.A. Olivieri, M. Behar, P.F.P. Fichtner, F.C. Zawislak, D. Fink* and J.P. Biersack

A pure KC1 single crystal and an A1/KC1 bilayer system consisting of a 600 X Al film evaporated onto a KC1 single crystal were both implanted with 300 keV of 2O9Bi+. The Bi depth profiles, in both systems, analyzed by the Rutherford backscattering (RBS) technique have shown very good agreement with the theoretical calcula'ions performed using the Monte-Carlo TRIM simulation code . Thermal annealings of both samples were performed at 200, 300, 400, 450 and 500 °C for 1 hour, in order to follow the diffusion behaviour of the -17-

implanted Bi into the homogeneou and bilayer systems. At variance with what 2) was observed for the Al/Ti system , the behaviour of the implanted ions was reproduced by a regular thermal diffusion mechanism. For pure KC1, it was found that Bi diffuses in accordance with the relation D • 1.25 x 10 exp -0.24 eV/KT. Instead for the A1/KC1 compound the Bi diffuses into the KC1 following the relation D « 2.5 x 10" exp -0.24 eV/KT. The difference of almost one order of magnitude between both diffusion coefficients indicates that the interface acts as a trap for the implanted ions.

*Hahn-Meitner-Institut ftlr Kernforschung Berlin, West Germany. 1) J.P.Biersack and L.G.Haggmark, Nucl. Inst. and Methods _T74_ (1980) 267. 2) Described elsewhere in this report.

Q Range and Range Straggling of 15 to 350 keV Ga in Amorphous Silicon* P.F.P. Fichtner, CA. Olivieri, J.P. de Souza, M. Behar, F.C. Zawislak, D. Fink+ and J.P. Biersack*

We report here a set of accurate measurements of projected ranges (R ) and projected range stragglings (AR ), performed by using the Rutherford back- go P scattering technique for Ga implanted into amorphous silicon. The implanted energy range vary between 15 and 350 keV. The experimental results are compared with the theoretical predictions performed by the Monte-Carlo TRIM method, using the new universal potential and refined electronic stopping power. The agreement between experiment and theory is excellent for both the R and AR values, fact that gives further support to the theoretical assumptions underlying in the TRIM program.

•Radiation Effects Letters 85 (1984) 117. •Hahn-Meitner-Institute fUr Kernsorschung Berlin, West Germany. -18-

Adhesion Enhancement Induced by MeV Ion Beams**

R.P.

Enhancement in adhesion of thin Au films on vitreous SiO~ and GaAs 35 substrates was induced by a Cl ion beam at energies between 6.5 and 21.0 MeV 12 2 15 2 and doses from 10 ions/cm to 10 ions/cm . The enhanced adhesion was studied by using the "Scotch Tape" and the "Scratch" tests. For Au on vitreous

SiO? it was found that the film passes the "Scotch Tape" test in two different 13 2 dose ranges; one at low dose centered around 10 ions/cm and almost independent of ion beam energy, the other at higher dose and more strongly dependent on the beam energy. In the case of Au film on GaAs, in order to study the role of the electronic properties on the enhancement in adhesion, wafers with four different dopants (Cr, Si, Te, and Zn) were used and very different adhesion modifications were found depending on the dopant.

*To be published in Nuclear Instruments & Methods. +Work performed at Div. of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, California 91125, USA. ++On leave from Instituto de Física-UFRGS, Brazil.

High Sensitivity Carbon Content Analysis of Geological Materials Using 1.4 MeV Deuterons*

Rogério P. Livi , Marcus H. Mendenhall, T.A. Tombrello, Gerald Fine and Edward Stolper Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, CA 91125, USA.

12 13 High pressure albite glasses have been analyzed using the C(d,pQ) C nuclear reactions. By using 1.4 MeV deuterons, a detection limit of 100 ppm by weight of carbon can be easily achieved in a 10 minute irradiation of a sample using 15 nA of beam, thus minimizing radiation damage to the sample. Absolute calibration can be obtained either by using the known cross section or by working against a standard. Working at this energy provides sensitivity -19-

primarily at depths from 1 to 4 microns, so moderate levels of surface con- tamination can be tolerated.

•Contributed paper at the Int'l Symp. on "Three-Day in Depth-Review on the Nuclear Accelerator Impact in the Interdisciplinary Field", May 30-June 1, 1984, Italy. •On leave from Instituto de FÍsica-UFRGS, Brazil. ••••i-Division of Geological and Planetary Sciences, CALTECH, Pasadena, CA 91125.

Heavy Ion Rutherford Scattering for Measurement of Heavy Element Concentrations and Isotopic Ratios*

Marcus H. Mendenhall+, Rogério P. Livi++ and T.A. Tombrello*

Work is currently being done at Caltech to extend the sensitivity limits of RBS techniques. For example, by using 4 MeV Cl ions, one can look at heavy 9 2 element (e.g., Pb or U) surface concentrations of 10 /cm on light substrates (e.g., Al or Si) while minimizing detector damage and dead time. This is being used to study archeological, mineralogical, and mcteoritical materials. We are also using oxygen, fluorine, and carbon backseattering to do isotopic ratio measurements; one example is its use for the measurement of isotopic frac- tionation induced by ion beam sputtering. At present, we can separate one mass unit at mass 63(Cu); soon it should be possible to separate one mass unit at masses greater than 100.

•Contributed paper at the Int'l Symp. on "Three-Day in Depth-Review on the Nuclear Accelerator Impact in the Interdisciplinary Field", May 30-June 1, 1984, Italy. +Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, CA 91125, USA. ++0n leave from Instituto de Física-UFRGS, Brazil. -20-

Electrical Contact and Adhesion Modification Produced by High Energy Heavy Ion Bombardment of Au Films on GaAs*

R.P. Livi+, S. Paine3, C.R. Wie, M.H. Mendenhallb, J.Y. Tangc, T.Vreeland, Jr., and T.A. Tombrello Divisions of Physics, Mathematics, and Astronomy and Engineering and Applied Science, CALTECH, Pasadena, CA 91125, USA

Thin gold films over GaAs wafers with different dopants (Cr, Si, Te, and Zn) were used to study the role of the substrate electronic properties in the electrical contact and adhesion modification induced by MeV/nucleon heavy ion bombardment. The enhanced adhesion was studied using a scratch test; the results show very different modifications of adhesion depending on the bulk electronic properties of the substrate. The sample with a Cr compensation doped substrate showed enhancement in adhesion for beam doses as low as 12 2 10 ions/cm , but Si and Te doped (n - type) substrates showed a sudden 14 2 enhancement in adhesion for doses around 10 ions/cm . Samples with Si and Te dopes substrates were used to study the bombarding ion dE/dx dependence of the 19 I 35 induced adhesion for _Fjf and Cl ions with electronic stopping power ranging from 161 eV/A* to 506 eV/Ã*. In this range the dose threshold for the onset of induced adhesion has a power law dependence, D * D_(dE/dx) *

*To appear in the Proceedings of the 1984 Materials Research Society Meeting. Boston, November 26-30, 1984. +0n leave from Instituto de Física-UFRGS, Brazil. a) Dept. of Electrical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. b) Phys. Dept., Vanderbilt University, Nashville, Tennessee 37235, USA. c) Nucl. Phys. Division, Fudan University, Shanghai, People's Republ. of China.

Two Types of MeV Ion Beam Enhanced Adhesion for Au Films on Si.üo

C.R. Wie, C.R. Shia, M.H. Mendenhall, R.P. Livib, T. Vreeland, Jr.c and T.A. Tombrello Division of Physics, Mathematics, and Astronomy, California Ins- titute of Technology, Pasadena, California 91125, USA

The ion beam-enhanced adhesion of thin Au films on vitreous silica substrates was studied for a wide range of Cl ion beam doses for beam energies between 6.5 MeV and 21.0 MeV. Since the residual adhesion of Au on SiCL is low, -21-

the improved adhesion can be easily seen using the Scotch Tape Test. The threshold in the enhanced adhesion corresponding to passing the tape test occurs at two different dose ranges for a given energy; one at very low dose 13 2 centered around 1 x 10 /cm , the other at higher doses with a threshold of around 1.5 x 10 /cm (depending upon the beam energy). At low doses (2x10 15 2 to 5x10 /cm ) surface cracks occur on the SiO. substrates, these cracks close 13 2 up at doses higher than 5 x 10 /cm . A possible explanation of the low dose range enhanced adhesion is associated with the surface crazing of the ^ substrate. To make the adhesion test more quantitative, a scratch test was also used on the samples. a) Nuclear Research Institute, Lanzhou University, China. b) On leave from Instituto de Física-UFRGS, Brazil. Fellowship from CNPq, Brazil. c) Division of Engineering and Applied Science, Caltech, USA.

Ion Implantation Metallurgy**

I.J.R. Baumvol

We describe some current applications of Ion Implantation in surface engineering. We discuss in detail the use of Ion Implantation as a coating method for portection of metallic engineering components against wear, fatigue and corrosion. Other potential applications of Ion Implantation in metallurgy are considered here. We discuss also in this chapter the present trends on the use of Ion Implantation on the metallurgical industri, specially those concerning the cost of the method and the alternatives to lower it.

*Work supported by CNPq and PINEP. +In "Ion Implantation: Science and Technology", J. Ziegler (ed.), Academic Press (1984). -22-

Recoil Implantation of Antimony into Silicon by Argon Ion Bombardment**

R. Erichsen Jr., I.J.R. Baumvol and J.P. de Souza

We report here on recoil implantation of antimony atoms from a 60 no thickness film deposited on a silicon substrate. The experiments were performed in order to investigate the influence of different implantation parameters on Che yield and depth profile of the recoiling antimony atoms. We have used Ar energies between 40 and 800 keV, doses between 1x10 and 1x10 cm" , sample temperatures between 20 and 300 C and dose rates between 1 and 20 pA-cm" . Another aspect considered here was the process removal of the remaining film. We studied the influence of different conditions of film removal on the recoil yield. The results of the present work indicate that the recoil yield is a function of the energy and total dose of the bombarding ions. Furthermore, no variation with the Ar dose rate or with the sample temperature was observed. The antimony recoil depth profile depends mainly on the total dose of Ar+ and does not depend on its energy, dose rate or target temperature during implan- tations.

*To be published in Nucl. Inst. Methods. •Work supported in part by CNPq and FINEP, Brazil. -23-

Properties of the Pure Heusler Phase of the Cu?MnSn Alloy**

H.I. da Costa Jr., M.A.Z. Vasconcellos, J.V. Kunzler and M.N. Baibich

The Cu_MnSn Heusler alloy, which is traditionally obtained as a mixture of the true magnetic L2 structure and the non-magnetic A2, can have the concentration of the later phase reduced by increasing the quenching rate when solidifying the samples. This can be achieved using our "melt-spinning" device at different conditions of wheel speed and pressure differential. The presence of small inclusions of A2 phase were monitored by MHssbauer soectroscopy as well as X-Ray diffractometry. Analyzing both the unsplit Müss- bauer absorption line and the X-Ray spectra, the fraction of A2 phase in the final sample can be evaluated. Using this information and the value of the electrical resistivity for the pure A2 phase, one can establish the value for the resistivity of the L2 phase once the value for the mixture is known. Systematic changes in A2 phase concentration allow for an internal check of the effective medium calculation used, similar to those used to evaluate the conductivity of heterogeneous mixtures. Our preliminary results in two concentrations are encouraging

*Published in Summary form only in Ciência e Cultura 36(7) (1984) 304. +Work supported in part by CNPq, FINEP, PROPESP-UFRGS.

Magnetoelastic Properties of ErFe~

J.B.M. da Cunha, P.J. Viccaro and J.E. Schmidt

The intennetallic compound ErFe. has a magnetic transition at 47 K which is the result of the competition of anisotropy fields of the atoms at different sites of the crystal structure. This transition is accompanied by a spin rotation which disturbs the magnetoelastic properties of the system. The measurement of the linear magnetostrii cion revealed a large peak at 47 K associated with the spin rotation. We are presently trying to interpret the data assuming that the energy of the system attains a new minimum which involves necessarely a deformation of the crystal. The results are going to be compared with the analysis made of MtJssbauer effect* on the same sample.

*J.B.M. da Cunha, Thesis work. -24-

Macroscopic and Microscopic Magnetism of Amorphous Metal-Metalloid Alloys*4"

M.A.Z. Vasconcellos, P.F.P. Fichtner, R.P. Livi, M.I. da Costa Jr. and M.N. Baibich

Müssbauer effect and magnetization of amorphous (Fe Ni )ar,B9n ribbons were measired to check the interrelation between macro and microscopic magnetic phenomena. The ribbons were obtained by melt spinning at a constant cooling rate and were studied under X Ray diffractometry. The MHssbauer effect spectra show a distribution of hyperfine fields on the Fe site, as well as a possible isomer shift distribution. The hysteresis loops obtained from toroids made from the ribbons were calibrated against that of 5N pure Ni, and show no direct correlation of the saturation magnetization with the hyperfine field on the Fe site. This implies that the local field involves other contributors than the macroscopic magnetization and that no significant composition fluctuations are present (such as clusters).

*Work supported in part by CNPq, FINEP, PROPESP-UFRGS. +To be published in the Annals of I Simpósio Latino-Americano de Física dos Sistemas Amorfos (Niterói 1984), Supplement to Revista Brasileira de Física.

Results and Ideas of Electronic Transport in Amorphous Metals**

Mario N. Baibich

In this work we have presented a collection of significant results and ideas in the field with no intention of being complete. The objective of this work was to introduce the beginner to the myriad of publications about this subject, with great stress on the phenomenological aspects. We have treated the electrical resistivity, magnetores istance, thermopower, pressure effects on the resistivity, magnetism, magnetostriction, density of states, specific heat, superconductivity and crystallization in glassy metals.

*Work supported in part by CNPq, FINEP, PROPESP-UFRGS. +To appear in the Annals of I Simpósio Latino-Americano de Física dos Sistemas Anorfos, Niterói, RJ, 1984. Supplement to Revista Brasileira de Física. -25-

The Role of Zr in Electronic Transport of Aaosphous CuZr*+

M.N. Baibich

Using experimental results for the electrical resistivity of amorphous Cu, .Z alloys, we have calculated the term r for the expression of the thermopower according to the extended Faber-Ziman theory for glassy metals. Scattering matrix formalism was used as well as the energy dependence of the phase shifts that generate the matrices. The results obtained are compared to the experiment and show that they do not obbey the same functional form as a function of composition, even if they are similar to those found for liquid metallic alloys. By a simple artifice we were able to see the relative importance of each 3e s of the contributions noting that the contribution of the term 13n2/ lz i- most important, indicating that Zr has a crucial role in the electronic behaviour of amorphous CuZr.

*Work partially supported by CNPq, F1NEP, PROPESP-UFRGS. +To appear in the Annals of I Simpósio Latino-Americano de Física dos Sistemas Amorfos, Niterói-RJ, 1984. Supplement to Revista Brasileira de Física.

Order-Disorder Transition in NiMn Alloys*

M.A.Z. Vasconcellos, J. Schaf, W.H. Schreiner and M.N. Baibich

The order-disorder transition of NiMn alloys was studied through electrical resistance measurements at high temperatures. Both isothermal and isochronal heating experiments were performed to establish the kinetics of that transition. The experiments clearly display the transition from long to short-range magnetic order. More experiments of the same kind are underway to determine an activation energy for the ordering process.

«Partial support by CNPq, FINEP and PROPESP-UFRGS. -26-

Magnetic Properties of Mixed System Pt,(Mn,Fe) *

W.H. Schreiner*, W. Stamm and E.F. WassermannT

Susceptibility, magnetization and time-dependent TRM measurements were performed on the pseudobinary Pt,(Mn, Fe ), 0 < a < 0.75 alloys. Cold worked alloys were also analysed. In the concentration range where mixed magnetism was expected a spin or clusterglas phase was identified. A detailed magnetic phase diagram can be drawn as a result of our measurements.

•Presented in part at the Spring Meeting of the DPG in MÜnster, West-Germany, partial support DAAD. +0n leave from IF-UFRGS, Brazil. tLabor für Tieftemperaturphysik Uni Duisburg-4100 Duisburg, Germany.

Electrical Resistivity of the Pt (MntFe) and the (Pt,Pd),Fe Alloys*

W.H. Schreiner and J.V. Kunzler

The electrical resistivity of the mixed magnetic systems Pt_(Mn,Fe) and (Pt,Pd).Fe was measured from 4 to 300 K. The curves show the p-anomalies which can be attributed to the magnetic transition temperatures and Pt-Mn- ,Fe. ,, which displays a spin-glass region, shows a strong minimum in its resistivity in accordance with other Pt based spin-glasses.

«Supported in part by CNPq and FINEP.

Electrical Resistivity of the Co^VAl Heusler Alloy*

W.H. Schreiner and J.V. Kunzler

The ferromagnetic Co~VAl Heusler alloy shows magnetic moments only on the Co atoms. Contrary to the "normal" Heusler alloys (X-YiO with Mn at the Y site Co.VAl is expected to behave as an itinerant ferromagnet. Curiously Co^VAl shows a strong resistivity minimum at 30 K. This is the first time that such a minimum was found in Heusler alloys. Measurements will be extended to other Co,YAl and Co^YGa alloys.

•Supported in part by CNPq and FINEP. -27-

Crystallization of Amorphous Pseudobinary Alloys Type

M.A.Z. Vasconcellos and M.N. Baibich

The crystallization kinetics of amorphous metallic ribbons type (Fe Ni ) B__, obtained in this laboratory, was studied using isochronous i—x x oQnu zu heating, at different heating rates. The crystallization temperatures were determined from the transition seen in the electrical resistivity. The different parameters obtained (resistivity, dp/dT and T ) are studied against the concentration. With this information and using the Johnson-Mehl- Avrami equations we determined the activation energies associated to the process of transition from the amorphous metastable state to the corresponding crystalline states.

«Work supported in part by CNPq, FINEP, PROPESP-UFRGS. +To be published in the Annals of 1 Simpósio Latino-Americano de Física dos Sistemas Amorfos (Niterói-RJ, Brazil, feb. 1984). Supplement to the Revista Brasileira de Física.

Magnetostriction of Pd-Fe Alloys

J.E. Schmidt* and L. Berger*

The linear magnetostriction X of polycrystalline Pd Fe alloys has S f—X X been measured as a function of alloy composition, at temperatures of 300, 77, and 4.2 K. The effect on A of atomic ordering of Pd-Fe and PdFe type ha» been investigated. The value of X is positive for x > 0.21, bat changes sign three tines in the composition range x > 0.21. This composition dependence can be understood semiquantitatively in terms of the simple split-band model, where iron and palladium each have their own d band, distinct on the energy scale. Contributions to A from electrons of both spin directions have been included. Best fit between theory and data is obtained for a value of the deformation potential of d electrons equal to -0.6 eV. The anomalous Hall effect and the g factor of Pd-Fe are also discussed in the light of the split-band model.

*0n leave from I7-UFRGS, Brazil. +Physics Department, Carnegie-Mellon University, Pittsburgh, PA 15213, USA. tJ. Appl. Phys. 55(4) (1984) 1073. -28-

Activation Energies for Crystallization of Amorphous Metals*

M.A.Z. Vasconcellos and M.N. Baibich

The study of crystallization behaviour of amorphous metals has been made traditionally by means of two methods. One is that of isothermic anneals at different temperatures, from which, by the use of Johnson-Mehl-Avrami equation one obtains both the activation energy for the transformation (AE.) and the dimmensionality (n) of crystal growth within the sample(1 ). The other method is to heat the samples at different constant heating rates and treat (2) the data according to Kissinger , thus extracting the activation energy

We are, at present, concluding some measurements on the crystallization

behaviour of a series of (FeNi)80B20 amorphous alloys as a function of Ni content using both methods cited above. The samples were made by us in this laboratory by "melt-spinning" from approximately the same temperatures for all concentrations. The crystallized fraction is measured using electrical resistance as a probe with a DC bridge described in this Progress Report. The transformed fraction is calculated from an effective meaiurn calculation, considering that the resistivity is approximately a linear function of crystal content in the sample. Preliminary results show that both methods are consistent and that addition of Ni increases the activation energy for the process even if the crystallization temperature is reduced. We have also seen some structure relaxation effects at low temperature which led to a new project studying these effects only.

References: (1) M.N. Baibich et ai, J. Appl. Phys. 52, n9 3, (1981) 1886. (2) H.E. Kissinger, Anal. Chem. 29 (19577 1702.

*Work supported in part by CNPq, FINEP, PROPESP-UFRGS.

Electrical Resistivity of the Ni^Mnln Heusler Alloy*

G.L.F. Fraga, J.V. Kunzler, F. Ogiba and D.E. Brandão

Electrical resistivity and saturation magnetization measurements were performed on the «i-Mnln Heusler alloy, in the temperature range of 4-300 K. -29-

The experimental data clearly show the existence of a unique resistivity behaviour for 7 Z T i. 20 K, described by an aTn-lav. Intermediate temperature 2 data, 170 i T £ 300 K, obey an AT+BT phenomenological fitting and are veil described in terms of electron-phonon and spin-disorder scattering.

*Phys. Stat. Sol. (a) 83 (1984) K187.

Spin-Disorder Resistivity in the Ni_Mn(Sn, In ) Heusler Alloys* *L 1 •"X X G.L. Fraga, J.V. Kunzler and D.E. Brandão

Electrical resistivity measurements have been performed on the Ni-MniSn In ) Heusler alloys, where x = 0; 0.02; 0.05; 0.10 and 0.15, in ** I ~X X the temperature range of 4-300 K.. The experimental data clearly show the existence of two distinct resistivity behaviours, both described by an aTn-law, for 7 < T < 20 K. Between 170 and 300 K the data are well described by an 2 AT + BT phenotnenological fitting and the obtained results are in good agreement with an interpretation in terms of electron phonon and spin-disorder scattering.

*To appear in Phys. Chem. Sol.

The Effects of the Chemical Order-Disorder on the Magnetic Anisotropy of NiMn Spin Glasses J. Schaf* and P. Hippert

The magnetic behavior of highly disordered samples is found to be identical to the well known CuMn or AgMn spin glasses. Magnetization, Suscep- tibility and Torque measurements after the field cooled or zero-field cooled state of a same specimen show a net, systematic and reversible effect of the chemical order on the anisotropy. This behavior is tested at different measuring temperatures. The quantitative behavior of the anisotropy energy is consistent with the predictions of Dsyaloshinsky-Moriya couplings.

*Work performed at Université de Paris-Sud-Orsay-France. •Université de Paris-Sud-Orsay-France. -30-

Spin-Glass Behavior as a Function of Concentration and Local Order by NMR in Nearly Random NiMn Systems*

J.Schaf++, K. Le Dang++ and P. Veillet++

Unidirectional anisotropy fields (H.) in disordered Ni.nn Mn (25Sr.S32) systems after field cooling are found by NMR (spin echo) to be very sensitive to the Mn concentration and to local order. The H. increases by roughly a factor of 10 when the concentration increases 5Z. The Mn NMR spectra show that all Mn have several first nearest Mn neighbours. For a given concentration, in the above range, the H are very sensitive to the annealing-quenching temperatures (T.A) and vanish when the sample is cooled down from 9C0 C in 2 h. The NiMn system can be tuned by heat treatments from spin-glass to a ferromagnet. The Mn NMR spectra with decreasing T. show a clear metallurgical evolcion tending to states where a Mn atom sees fewer first nearest Mn neighbours. We find evidence that the anisotropy has its roots in atomic randomness.

*Journal of Magnetism and Magnetic Materials 3]_ (1983) 297. +0n leave from IF-UFRGS, Brazil. "•Physique des Solides, Université Paris-Sud, 91405 Orsay, France. ++Institut d'Electronique Fondamentale, Université Paris-Sud, 91405 Orsay, France.

Extended and Local Effects of Cold Work in Heusler Alloys*

J.Schaf++, K. Le Dang++, P. Veillet++ and I.A. Campbell1"

We find from NMR (spin-echo) and x-ray diffraction that plastic deformations during cold work introduce many dislocations and associated lattice deformations in a number of Heusler alloys: Pd.MnSn, Pd-MnSb, Cu-Mnln, Cu.MnAl, NijMnln, Pd»MnIn and NiMnSb. In Pd~MnSn these effects are very important and result in atomic disorder. In other alloys cold work produces distortions but apparently no atomic disorder. The strong effects of cold work on Heusler alloys (L2. structure) contrast with almost unobservable effects in the C1, structure alloy NiMnSb.

*J. Phys. F: Met. Phys. _H (1983) 1311. +0n leave from IF-UFRGS, Brazil. tPhysique des Solides, Université Paris-Sud, 91405 Orsay, France. ++Institut d'Electronique Fondamentale, Univ. Paris-Sud, 91405 Orsay, France. -31-

NMR and Magnetization Study of the Mixed Systems (Pd Cu )_MnIn

and (PdlxNix)2MnIn*

J. Schaf++, I.A. Campbell*, K. Le Dang++, P. Veillet++ and A. Hamzik

Systematic NMR and magnetization data with concentration show that for decreasing x these systems go from ferromagnetic (F) to anti-ferromagnetic (AF) order by passing a mixed phase region where both magnetic orders coexist in different domains. The magnetic phase diagrams for both alloy series are nearly coincident. The NMR spectra show that the Cu or Ni atoms substitute randomly onto Pd sites and we find no evidence that the participation of Mn atoms in F or AF domains is at all correlated with their nearest neighbour environments. In the limit where the AF order becomes largely dominant the samples exhibit a magnetic anisotropy after field cooling.

*Journal of Magnetism and Magnetic Materials 36^ (1983) 310. +0n leave from IF-UFRGS, Brazil. tLaboratoire de Physique des Solides, Université Paris-Sud, 91405 Orsay, France. ++Institut d'Electronique Fondamentale, Université Paris-Sud, 91405 Orsay, France. §Physics Department, Faculty of Natural Sciences, Institute of Physics of the University of Zagreb, Zagreb, Yugoslavia.

Magnetoresistance of Pd-Fe and Pd-Ni-Fe Alloys*

Y. Hsu+, J.E. Schmidt , M. Gupta*, S. Jen+ and L. Berger+

The electrical resistivity of Pd-Fe alloys has been measured in magnetic fields parallel and perpendicular to the current, for a wide range of alloy compositions. The influence of atomic ordering on the magnetoresistance has been investigated. The ferromagnetic anisotropy of resistance Ap/p reaches a maximum value of +97. in the ordered state between 30 and 35 at.2 Fe, and +6% in the disordered state between 40 and 60 at.% Fe, at 4.2 K. At 295 K, Ap/p never exceeds +1%. Similar measurements have been done on

(PdeQNic0)1OQ_ Fe for x á 30 at.% Fe. The maximum Ap/pQ value of +77. is obtained for 10 at.% Fe at 4.2 K.

*J. Appl. Phys. 54(4) (1983) 1887. •Physics Dept., Carnegie-Mellon University, Pittsburgh, PA 15213, USA. tOn leave from IF-UFRGS, Brazil. -32-

Birefringence in Optical Coatings**

l.J. Hodgkinson , F. Horowitz , H.A. Macleod , M. Sikkens and J.J. Wharton

Experiments carried out on evaporated thin-film coatings show that the coatings are birefringent. In general the relative anisotropy in the refractive index amounts to a few per cent. The magnitude of the anisotropy indicates that it has to be attributed to form birefringence, related to the columnar microstructure of the films. For normally incident light, this birefringence becomes noticeable only in coatings that are obliquely deposited. For example, in a zirconium oxide-silicon oxide narrow-band filter deposited at 30 deg, the transmission peak shifts 40 A when the polarization direction is rotated. Slight birefringence has also been observed in coatings rotated during deposition for uniform thickness and can be attributed to a nonzero mean deposition angle. All dielectric materials studied have been found to be biaxial. Experimental techniques have been developed to measure the three refractive indices of the birefringent films. Qualitatively, the birefringence can be explained from the microstructure of the films, assuming the voids between the columns to be elongated in the direction perpendicular to the plane defined by the vapor beam and the substrate normal. Computer simulations of the film growth are used to obtain a more quantitative description of the birefringence.

*J. Opt. Soc. Am., Vol. 73, p. 1871 (1983). +Work supported in part by a Defense Advanced Research Projects Agency/NWC contract. tOptical Sciences Center, University of Arizona, Tucson, Arizona, USA. ++0n leave from Instituto de Física-UFRGS. Sponsored by CNPq, Brazil. {The author gratefully acknowledges the support of the Netherlands Organi- zation for the Advancement of Pure Research.

Form Birefringence in Thin Films*

F. Horowitz* and H.A. Macleod++

We consider in this work the anisotropic microstructure contribution to the polarization effect in thin films deposited at high angles of vapor incidence. Previous reports that metal films mainly respond as polarizers under -33-

such conditions have been confirmed. Structural anisotropy in dielectric films, rather than affecting the extinction coefficient values differently along different directions, seems to induce significant asymmetry in the refractive index values that enables us to find a retarder-like behavior. Quan- titative analysis of the effect under normal incidence light at 632.8 nm is presented for aluminum and zirconium oxide films, and its structural origin is discussed.

•Published in the Proc. S.P.I.E., vol. 361 (1984) p. 83. +0n leave from Instituto de Física-UFRGS. Sponsored by CNPq, Brazil. ++Optical Sciences Center, Univ. of Arizona, Tucson, Arizona 85721, USA.

Computer Simulation of Thin Film Growth: Applying the Results to Optical Coatings*

Marten Sikkens , Ian Hodgkinson, Flavio Horowitz , Angus Macleod and John Wharton Optical Sciences Center, Univ. of Arizona, Tucson, AZ 85721, USA

Computer simulation of thin film growth has been used extensively to gain insight into the origin and nature of the microstructure of vapor deposited thin films. Usually, however, no attempts are made to predict film properties other than column angle and film density from such simulations. The aim of our work is to derive quantitative data from computer simulations in order to be able to predict relevant properties of optical coatings. The deposition of 2,500 - 25,000 particles has been simulated on a computer by random deposition of two dimensional hard discs, using a simple relaxation scheme. Statistical analysis of the results yields quantitative data for the density, column angle and column period. On the basis of these results, a simple model has been developed for the microstructure of a three dimensional film. The birefringence and the shape of water penetration fronts in evaporated optical coatings, predicted from this model, are confirmed by experiment.

*To be published in Proc. SPIE, 1984. a) Dept. of Applied Phys., Univ. of Groningen, The Netherlands. b) Dept. of Phys., Univ. of Otago, Dunedin, New Zealand. c) On leave from Instituto de Física-UFRGS. Sponsored by CNPq, Brazil. -34-

Deposition, Characterization, and Simulation of Thin Films with Form Birefringence*

M.R. Jacobson**, F. Horowitz and Bagjun Liao

Birefringence in optical thin films due to structure on a scale large compared to atoms but small compared to optical wavelengths, known as form birefringence (FB), was observed almost a century ago. More recently, studies of obliquely deposited metal films stimulated new interest in birefringent films. The link between structure, which is predominantly columnar in evaporated thin films and birefringence has been conclusively demonstrated through ellipsometric measurement and modeling. Direct measurements of form birefringence are especially laborious in tilted dielectric films, since essentially four quantities must be derived: three indices of refraction and the film thickness. Clearly, four measurements are required; Horowitz used an ellipsometric method to perform such measurements on a zirconium oxide (ZrO,) film. Later, a 4.6-um-thick film of ZrCL was obliquely deposited; spectrophotometric measurements revealed its utility as a half-wave plate. A parallel effort directed at understanding FB films through computer simulations has been undertaken by Sikkens and Liao. These simulations can be specialized to include defects, epitaxy, and anisotropic surface mobility. Applications of obliquely deposited FB films of familiar thin film materials can be anticipated if their structure and performance can be more thoroughly understood.

*Accepted for publication in Proc. SPIE, 1984. **Optical Sciences Center, University of Arizona, Tucson, AZ 85721, USA. •On leave from Instituto de FÍsica-UFRGS, Brazil. ++Visítíng from the Shenyang Institute of Technology, Shenyang, Liaoning, PRC. -35-

A Grazing Incidence Dye Laser with an Intracavity Lens*

J.A. Lisboa, S.R. Teixeira, S.L.S. Cunha, R.E. Francke and H.P. Grieneisen

Nitrogen pumped tunable dye laser has become an important light source for laser spectroscopy because of its simplicity and low cost. Hansch demonstrated for the first time a narrow linewidth operation of this laser using an intracavity telescope. However, this kind of laser requires a precision ad- 2 justment of the grating mount although it is quite efficient. Shoshan and others devised a new dye laser cavity dispensing of the telescope and using the grating at grazing incidence. An appropriate mirror provides the required feedback toward the gain region. Although the alignment of this laser is much simpler than that of the HMnsch type, its overall efficiency is quite low due to poor coupling between the light feedback from the mirror-grating combination and the gain region of the dye cell. We proposed and tested the use of an intracavity lens so as to improve the coupling efficiency of the light in the dye laser cavity. Using an holo- graphic grating with 2400 1/iran, 56 mm useful length and an intracavity lens with a focal length of 24 mm, we achieved a linewidth of 1.1 Ghz (FWHM). The lens was at 34 mm from the output of the dye cell and at 55 mm from the center of the diffraction grating.

*Opt. Comm. 44 (1983) 393. 1. T.W.HHnsch, Appl. Optics, J^ (1972) 895. 2. I.Shoshan, N.N.Danon and U.P.Oppenheim, J. Appl. Phys. 48 (1977) 4495. 3. S.Saikan, Appl. Phys. VJ_ (1978) 41. 4. M.G.Littman and H.J.Metcalf, Appl. Opt. ^7 (1978) 2224. -36-

Extended Linear Tuning of a Dye Laser with Intracavity Fabry-Perot and Diffraction Grating

M.R. 01cay, J.A. Pasqual and R.E. Francke

Nitrogen pumped dye lasers are widely used light sources in spectroscopic studies because of their simplicity, high power and low cost. À large effort .12 3 has already been devoted to achieve an efficient, narrow linewidth ' ' and easily tunable dye laser. The most comnon dye laser configuration uses a diffraction grating and Fabry-Perot interferometer and their linewidth is generally Fourier-Transform limited. The tuning of this kind of laser was 4 considered difficult because the dispersive characteristics of the Fabry-Pe- rot interferometer and those of the diffraction grating are different. In this work it is shown that the tuning can indeed be linearized and a system was built that can be tuned over an extended region without mode hopping. This system was tested by measuring the spectra of Iodine and it was found that it reproduces the known Atlas . The resolution of our present system is 600 MHz and is limited by acoustic noise.

1. R.Wallenstein and T.W.Hansch, Opt. Comm. V± (1975) 353. 2. T.Suziki, H.Kato, Y.Taira, Y.Adachi, N.Konishi and T.Kasuya, Appl. Phys. V\_ (1981) 331. 3. J.A.Lisboa, S.R.Teixeira, S.L.S.Cunha, R.E.Francke and H.P.Grieneisen, Opt. Connn. 44_ (1983) 393. 4. M.Hercher, Appl. Opt. £ (1969) 1103. 5. S.Gerstenkorn et P.Luc, "Atlas du Spectre d'Absorption de la Molecule d'lode", Editions du CNRS (1978), Paris, France.

Atlas of the B-X Absorption Transition of Molecular Iodine

Thomas Braun

Absorption bands of molecular iodine, I,, in the 20000 to 11000 cm spectral region have been measured with an accuracy better than 0.001 cm" . As this spectra was generated very easily with laser techniques it became a secondary wavelength standard in that part of the spectrum. Certain applications do require a knowledge of the specific transitions involved in each peak of that spectrum . Since an Atlas including the identification of such transitions was not yet available in the literature, we developed a computer program to generate that Atlas from 15000 to 18500 cm" . The -37-

referred Atlas includes the specific transition, energy of the lover level, transition moments and other spectroscopic quantities. The Atlas is distributed in five volumes and took 60 days of calculations on a TRS-80 microcomputer. Copies are available from the author.

Feco-Based Observations of Birefringence at Normal Incidence in Optical Coatings I.J. Hodgkinson*, F.Horowitz**, H.A. Macleod, M. Sikkens* and J.J. Wharton** University of Arizona, Optical Sciences Center, Tucson, AZ 85721

Structural anis>otropy occurs in evaporated thin films when the condensing molecules have insufficient mobility to form a tightly packed arrangement. Shadowing causes the growth of columns which are visible in electuon-micro- graphs of thin film sections and, in the case of deposition at an angle 5, tend to grow towards the source at angle tan" (ytanó). In this note we discuss measurements of birefringence made at normal incidence on a number of thin film materials which were deposited obliquely.

*Univ. of Otago, Dept. of Physics, Dunedin, New Zealand. **0n leave from Instituto de Fisica-UFRGS, Brazil. +Univ. of Groningen, Dept. of Appl. Phys., Nyenborgh 18, 9747 A6 Groningen, The Netherlands. ••-•Air Force Institute of Technology, AFIT/ENP Wright Patterson AFB, Ohio 45433.

Measurement of the Principal Refractive Indices of Thin Films Deposited at Oblique Incidence I.J. Hodgkinson*, F.Horowitz*, H.A.Macleod, M.Sikkens and J.J. Wharton+ Optical Sciences Center, Univ. of Arizona, Tucson, AZ 85721, USA

Shadowing causes form birefringence in optical thin films which are deposited at oblique incidence. For light incidence in the plane containing the direction of deposition and the substrate normal, the TE and TM polarizations in th« fila are decoupled and field transfer can be described using -38-

2x2 matrices. The three principal indices of birefringent films are deduced from measurements made on narrow-band interference filters. In one example refractive indices of 2.688, 2.429, and 2.452 were computed for Ti-O., deposited at 27 to the substrate normal. Both Ti^O, and ZrO? behave as positive biaxial media.

*Dept. of Physics, Univ. of Otago, Dunedin, New Zealand. +0n leave from Instituto de Física-UFRGS, Brazil. §Univ. of Groningen, Dept. of Applied Physics, Nyenborgh 18, 9747 A6 Groningen, The Netherlands. tAir Force Inst. of Technology, AFIT/ENP Wright Patterson AFB, Ohio 45433, USA.

Determination of Principal Refractive Indices of Birefringence Thin Films*

F. Horowitz and H.A. Macleod

Virtually all vacuum-deposited films present preferential orientations in their microstructure. In 1960, a revision of experiments performed for a de- cade lead to the conclusion that the granular structure of the films was the main cause for the anomalies observed in their optical constants . Improved deposition parameter control, thickness monitoring and characterization techniques, microfractography in particular, have turned this materials aspect 2 into the main problem in optical coatings today . We consider in this work a method for the characterization of an anisotropic film that takes explicitly into account its columnar microstructure. A biaxial dielectric film is taken with the assumption that it can be completely specified by its physical thickness d and a set of three refractive indices {n., n_, n,}, each along one of the principal axes of the material. Our method consists of determining those four parameters from the experimental observable s {A , A , <|i , 6 }, defined below through a properly developed theoretical S_ u t o framework . Prior to observation, the film is obliquely deposited at a known angle of vapor incidence on a partly masked substrate of known refractive index. 4 We then use two standard procedures in ellipsometry . After extinction is achieved, we obtain A. (optical path between the p and s-polarized modes) and tji (angular displacement of the analyzer transnission axis from the horizontal position, reduced to the first quadrant). These procedures have the advantage -39-

of high accuracy inherent to null measurements. The fourth observation utilizes the Abelês technique for its extreme simplicity, although Brewster's angle 9_ is located photoelectrically rather 6 than visually only . The polarimetrie extension of the technique as proposed by Hacskaylo is incorporated to increase further the accuracy of the measurement. For illustration we apply our method to the characterization of a zirconium oxide film deposited at 65° onto a glass substrate. The resulting param-

eters are: r^ » 1.502 (±0.009), n2 = 1.575 (±0.001), n3 = 1.788 (±0.015) and d « 602.5 (±0.6) nm. A simple model of the film microstructure is considered to interpret those results. The columns are taken as solid rods with infinite length, elliptical cross section, and with the refractive index of the bulk material, while randomly distributed in an air matrix. A plausibility argument is then presented that shows reasonable agreement between model predictions and measured values for the principal refractive indices.

1. Bousquet, P. and Rouard, P., J. Phys. Radium 2A_ (1960) 873. 2. Macleod, H.A., Proc. SPIE 32.5 (1982) 21. 3. F.Horowitz, Structure-Induced Optical Anisotropy in Thin Films, Ph.D. Dis- sertation, chapters 3 and 4. Optical Sciences Center, University of Arizona (1983). 4. Bennett, J.M. and Bennett, H.E. (1978). Section 10 in Handbook of Optics, W.G.Driscoll, ed. NY: McGraw-Hill. 5. Abelès, F., C. R. Acad. Schi. Paris 228_ (1949) 553. 6. Rally, J.C. and Heavens, O.S., Óptica Acta b_ (1959) 339. 7. Hacskaylo, M., J. Opt. Soc. Am. 54 (1964) 198.

+0n leave from Instituto de Física-UFRGS, Brazil. -M-Optical Sciences Center, Univ. of Arizona, Tucson, Arizona 85721, USA. -40-

Inductive Observation of Transitions from [100] Magnetic Domains to [010] and [001] in Silicon-Iron*

S.P. da Cruz and F.P. Livi

The transitions of magnetic domains from [100] to [010] and [001] directions were observed in silicon-iron sheets with Goss texture. The effects of applied field, mechanical stresses and angle 6 between field axis and [100) direction were studied. The transitions were detected inductively by a signal winding placed perpendicularly to the excitation winding. This choice was made in order to minimize the main flux contribution and maximize the signal from the transitions of interest.

In the figure are shown typical oscillographic records of signals obtained with 65 Hz excitation. The applied mechanical stress increases from left to right and favours the [100] •*• [010], [001] transition. The corresponding signal appears with an opposite sign as compared to the main flux contribution. This is due to the peculiar angle 6 for this sample. Our conclusion is that the transitions occur at field thresholds that depend on the angles and stresses involved. Relations between magnetocrystal line and magnetoelastic parameters 1 2 can be obtained. We also deduced that magnetic noises previously noticed ' have these transitions as origin.

1. V.A.Zaykova et al., Fiz. Metal. Metalloved, 4_3, 68 (1977). 2. A.J.Moses, IEEE Trans. Magn. MAG-17, 2872 (1981).

*Work partially supported by CNPq and FINEP.

Remarks on Alloying-Induced Lattice Parameter Changes in Inter- metallic Compounds*

L. Amaral, F.P. Livi and A.A. Gomes

The lattice parameter behaviour as a function of concentration in some (A. A') (B B1) rare-earth-transition metal and transition metal intermetallics, is qualitatively discussed in terms of the difference in -41-

d-occupation number of the A and B sites. Connections with other properties, magnetic in particular, are briefly mentioned, together with alloying induced lattice instabilities. A quite extensive series of experimental data is discussed within this simple model.

*Phys. Stat. So. (a) 80 (1983) 669. •••Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro, Brazil.

A Model for the E.Q.I, in High d-Density of States Metallic Systems*

L. Amaral, F.P. Livi and A.A. Gomes+

A model is formulated for the electric quadrupole interaction in d character metallic systems where the predominant contribution to the E.Q.I. is the electronic one. The behaviour of the E.Q.I, is shown to be determined by the relative occupations of the local d-sub-bands. The model adopts a tight binding approximation for the description of the electronic states and is well suited for intermetallic systems like Laves phases. As an illustration, some numerical results are shown for simple model band shapes.

•Published in An. Acad. Bras. Ciinc. 56 (1984) (1). •«•Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro, Brazil.

A Model for the Electronic Structure of (T T')Fe? Intermetallic Compounds: An Application to (Zr. Hf )Fe_

L. Amaral, F.P. Livi and A.A. Gomes

The electronic structure of pseudobinary (T T')Fe. compounds is studied using simple models, disorder being treated using the CPA. Two models are

proposed and applied to (Zr Hf )Fe?. We conclude that the 'reservoir* model is the more adequate for the series of compounds. The magnetisation and isomer shift data (measured at Fe sites) are calculated and the agreement with existing experiments is satisfactory. New experiments to confirm the predictions of the model are suggested.

*Centro Brasileiro de Pesquisas Físicas, CBPF/CNPq, Rua Xavier Sigaud, 150, 22290 Rio de Janeiro, RJ, Brazil. -42-

Mtíssbauer Study of Pseudobinary (Zr. Hf )Fe. Compounds

L. Amaral, F.P. Livi and A.A. Gomes

MHssbauer spectroscopy measurements were made at the Fe sites in the pseudobinary compounds (Zr. Hf )Fe-. The experimental results indicate the existence of two kinds of site with respect to isomer shift and quadrupolar interaction behaviour. An explanation based on a tight-binding model and taking into account the existence of a magnetisation axis along the <111> direction is presented for the observed hyperfine electric interactions.

•Centro Brasileiro de Pesquisas Físicas, Rio de Janeir, RJ, Brazil. RESEARCH IN THE FIELD OF THEORETICAL PHYSICS -44-

Lifetime of a Nuclear Hole state in a Field-Theoretic Model**

M.H. Steffani, M. Betz and Th.A.J. Maris

The lifetime of a hole state created in a quasi-free scattering experiment is calculated in a field-theoretic model of nuclear matter. In this model, the intermediate-range attraction and short-range repulsion present in the nuclear force are produced by the exchange of scalar and vector mesons, respectively. Nuclear properties are calculated in the mean-field approximation, suplemented by perturbative corrections. We calculate the imaginary part of the self-energy of a hole in lowest-order perturbation theory about the mean-field approximation. We find a large amount of cancelation between the contributions of scalar and vector meson exchanges, as occurs also in calculations of the imaginary part of the optical potential. The calculated widths are in reasonable agreement with experimental values. Although simple arguments indicate that exchange terms should not modify the results by more than about 25%, work is in progress to include them in the calculation.

^Presented at the V Encontro Nacional de Física de Energias Intermediárias, Gramado, RS (1984); to be published in Revista Brasileira de Física. •Work partially supported by FINEP and CNPq.

Bags in the Shell Model**

M. Betz, G. Krein and Th.A.J. Maris

For a Fermi sea of bag-like nucleons, the quark statistics leads to corrections which grow with the bag radius. The influences of this effect on the single particle nature of the sea and on the nuclear structure function F-(x) are estimated.

*Accepted for publication in Nuclear Physics. +Supported in part by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Financiadora de Estudos e Projetos (FINEP). -45-

Effective Polarization in Quasi-Free Scattering and Nuclear Structure**

C.A.Z. Vasconcellos, Th.A.J. Maris and C. Schneider

Theoretical predictions which have been experimentally confirmed have shown that the nucleon which is knocked-out in quasi-free scattering was in general polarized in the nucleus. This polarization which can be nearly complete, depends strongly on the structure of the initial and residual nuclei. Measurements of this polarization may therefore be used to discriminate between different models of these states. We have calculated in particular the effective polarization for the [jj] coupled shell model, [LS] coupling and a deuteron cluster model for the reactions Li(p,2p) He and N(p,2p) C. The distorted wave calculations have been performed in the WKB approximation with a square-well spin-independent nuclear optical potential, for 200 and 320 MeV incoming protons, in two different coplanar geometries. The calculated polarizations for these cases are very different, occasionally even in sign.

*Work presented at the V Encontro Nacional de Física de Energias Intermediá- rias, Gramado, RS (1984). To be published in Revista Brasileira de Física. +Work partially supported by FINEP and CNPq.

Recent Developments in Quasi-Free Nucleon-Nucleon Scattering**

P. Kitching++, W. I. McDonald**, Th.A.J. Maris and C.A.Z.Vasconcellos

The purpose of this paper is to give a brief review and to discuss some recent results of quasi-free scattering in a way which is understandable for a nuclear physicist without previous knowledge of the subject. After an introduction, a review of the theory is given. The spin dependence in (p,2p) scattering is considered in detail and a comparison of calculations and experimental results is made. The isospin dependence of the reaction is discussed. Finally a comparison with other quasi-free reactions and gome concluding remarks are presented.

^Accepted for publication in "Advances in Nuclear Physics. •«•Work Partially supported by FINEP and CNPq. ••University of Alberta, Edmonton, Alberta, Canada T6G 2J1. -46-

Mean Free Nucleon Path in Nuclear Matter

Th.A.J. Maris e G.I. Krein

The argument of Weisskopf explains how the Pauli Exclusion Principle strongly reduces the free nucleon-nucleon cross sections, leading to a long free nucleon path in nuclear matter. In this way the validity of the nuclear shell model becomes understandable. (2) We have calculated, in an earlier developed model , the mean free path of a bag-nucleon in nuclear matter. Because of the fact that the individual quarks obey the Pauli Principle the argument of Weisskop is not anymore directly applicable. For a bag of 1 fm radius we find a mean free path of 6 fm, which already severely interferes with the validity of the shell model. For appreciably larger bags this validity would be difficult to understand.

1. V.F.Weisskopf, Science JJKi (1951) 101. 2. M.Betz, G.I.Krein and Th.A.J.Maris, NucL. Phys. (accepted for publication).

KN Scattering in the Cloudy Bag Model: s, p and d-Waves**

E.A. Veit++, A.W. Thomas and B.K. Jennings Triumf, 4004 Westbrook Mall, Vancouver, B.C., Canada V6T 2A3

s, p and d-wave KN phase shifts are calculated with the cloudy bag model (CBM). The results are in qualitative agreement with phase shifts analysis, except in those partial waves where exotic resonances are claimed to exist. However it seems that it is possible to get good agreement for these waves by just playing with the CBM potential, without including explicitly exotic states.

*To appear in Phys. Rev. D. •This work was partially supported by NSERC (Canada), CNPq and FINEP (Brazil), ++On leave from IF-UFRGS, Brazil. tPhys. Depart., Univ. of Adelaide, Adelaide, South Australia, 5001. -47-

S-Wave Meson Nucleon Scattering in an SU(3) Cloudy Bag Model**

E.A. Veit , B.K. Jennings, A.W. Thomas and R.C. Barrett* Triumf, 4004 Wesbrook Mall, Vancouver, B.C., Canada V6T 2A3

The cloudy bag model (CBM) is extended to incorporate chiral SU(3)xSU(3) symmetry, in order to describe S-wave KN and KN scattering. In spite of the large mass of the kaon the model yields reasonable results once the physical masses of the mesons are used. We use that version of the CBM where the mesons couple to the quarks with an axial-vector coupling through the bag volume. This version also has a meson-quark contact interaction with the same spin flavour structure as the exchange of the octet of vector mesons. The present model strongly supports the contention that the A* (1405) is a KN bound state.

*To appear in Phys. Rev. D. •This work was partially supported by NSEBC (Canada), CNPq and F1KEP (Brazil), ++On leave from IF-UFRGS, Brazil. tPhys. Depart., Univ. of Adelaide, Adelaide, South Australia, 5001. ifrPhys. Depart., University of Surrey, Guildford, U.K., GU2 5XH.

Kaon-Nucleon Scattering in an Extended Cloudy Bag Model** •+ fé E.A. Veit , B.K. Jennings. R.C. Barrett and A.W. Thomas Triumf, 4004 Wesbrook Mall, Vancouver, B.C., Canada V6T 2A3

We describe low energy KN scattering by generalizing the cloudy bag model (CBM) to SU(3) chiral symmetry. We restrict our attention to I - 0, S-wave scattering. We obtain a reasonable fit to both the ill cross section in the region of the A* (1405) and low-energy kaon-nucleon scattering with strange- ness S - -1.

*Phys. Lett. 137B (1984) 415. •«•This work was partially supported by CNPq and F1NEP (Brazil), NSERC (Canada) and SERC (U.K.). ++0n leave from IF-UFRGS, Brazil. tPhys. Depart., University of Surrey, Guildford, U.K., GU2 5HX. $Phyc. Depart., Univ. of Adelaide, Adelaide, South Australia, 5001. -48-

Pion-Nucleon Scatterings Lengths in the Cloudy Bag Model*"*"

B.K. Jennings, E.A. Veit and A.W. Thomas Triumf, 4004 Wesbrook Mall, Vancouver, B.C., Canada V6T 2A3

We re-examine pion-nucleon S-wave scattering in the volume coupling version of the cloudy bag model (CBM). If the effects of multiple scattering are taken into account, one needs some phenomenological repulsive interaction in order to reproduce the experimental data. We parametrize this repulsion as a 20% increase in the pion mass inside the bag. It is argued that this relatively small change in mass provides strong, a posteriori support for the original assumptions of the CBM.

*Phys. Lett. 148B (1984) 28. +This work was partially supported by NSERC (Canada), CNPq and FINEP (Brazil), ++On leave from IF-UFRGS, Brazil. tPhys. Depart., Univ. of Adelaide, Adelaide, South Australia, 5001.

Excitation of Low-Spin (AN) States in C(p,d) C*

M. Dillig+, V.E. Herscovitz and M.R. Teodoro

Morris et al investigated the recoilless production of (AN) states in 12 C* at intermediate excitation energies. Around Ex = 240 MeV they found an unexpected structure in the exclusive C(p,dpp) Be cross section, possibly a signature of Gamow-Teller (AN) transitions of low multipolarity. If confirmed, this reaction not only provides rather direct information on the A-nucleus dynamics, it could also bridge the gap to the quenching of Gamow-Teller transitions at excitation energies far below the ir-threshold . We analyze the data from ref. 1 in a microscopic model. It involves, on the basis of effective Lagrangians, A rescattering via TT and p exchange, initial and final state interactions in the Eikonal approximation and conventional formfactors from shell model calculations. With the A-isobar treated in the closure approximation the model qualitatively accounts for the inclusive (p,d), (p,dp) and (p,dir) cross sections.

1. C.L.Morris et al., Phys. Lett, 123 B (1983) 37. 2. A.Richter, Nucl. Phys. A 374 (1982) 177 c.

*Proc. Intern. Conf. on Nucl. Phys., Florence, Italy (1983), C61, pg 379. tSupported in part by CNPq, FINEP (Brazil) and KFA (W.Germany). +Inst. for Theoretical Phys., Univ. Erlangen-Nürnberg, Erlangen, W. Germany. -49-

Multiple A(i236)-Rescattering in Nuclear Pion Absorption* M. Dillig+, V.E. Herscovitz and M.R. Teodoro

There is experimental evidence, that the nuclear absorption of pions around the 33-resonance involves considerably more than 2 nucleons, typically 3 to 5. We propose as a mechanism for the process an extension of the conventional tvo-nucleon absorption, invoking T and p induced A-isobar rescattering. A four-nucleon interaction is constructed in the framework of effective Lagrangians, with the parameters restricted from the pp •+• dv reaction; A propagation is treated in closure. A comparison of our model with a mechanism proposed by Brown et al, which proceeds via the formation of a AA-intermediate state is done.

*Supported in part by CNPq, FINEP (Brazil) and KFA (W.Germany). +Institute for Theoretical Physics, University of Erlangen-Nilrnberg, Erlangen, W.Germany.

A-Isobar Effects in Quasi-Free Scattering** M. Dillig++, V.E. Herscovitz and M.R. Teodoro

Quasi-free nucleon knock-out is conventionally treated as a genuine two- nucleon process, incorporating the 'hard' nucleon knock-out in the elementary NN t-matrix, while treating 'soft' multiple scattering corrections as initial and final state interactions via optical potentials. A more realistic description of these reactions, especially above the pion threshold, requires the inclusion of mesonic and isobaric degrees of freedom. In particular at higher energies, the influence of genuine three-nucleon mechanisms, induced by the excitation of the A(1236)-isobar close to its mass shell, is expected to be rather important.

*Proc. Univ. Alberta/TRIUMF Workshop, Studying Nuclei with Medium Energy Pro- tons, Canada (1983) p. 323-337. +Supported in part by CNPq, FINEP (Brazil) and KFA (W.Germany). •«••••Institute for Theoretical Physics, University of Erlangen-Ntlrnberg, Erlangen, W.Germany. -50-

Quark-Meson and Barion-Meson Couplings**

V.E. Herscovitz, M.R. Teodoro and M. Dillig •»

The formulation of TTNN coupling in Chiral Bag Models suggests as an ex-

tension a model for oNN and pNN couplings, where o and p couple via TTTT intermediate states. As an illustration, including in the baryonic sector qqq states below 1 GeV, low lying qq excitations and N and A with their experimental masses

(the OTTTT and PTTTT coupling constants being obtained from TTTT scattering data), the oNN form factor results smoother than in current meson-exchange models.

*Proc. IVth Bras. Meet. Part. & Fields, Itatiaia, Brazil (1983), 88-90. •Supported in part by CNPq, FINEP (Brazil) and KFA (W.Germany). ••Institute for Theoretical Physics, University Erlangen-NUrnberg, Erlangen, W.Germany.

Long and Intermediate Range Baryon-Baryon Interaction in the Chiral Bag Model*t

M. Dillig , V.E. Herscovitz and M.R. Teodoro

Chiral Bag Models have been fairly successful in describing gross properties of baryons, such as the pionic and kaonic cloud contribution to the magnetic moments. As a natural extension of this picture we formulate the coupling of heavier mesons, such as the o, p, u or the K*, via (correlated) multi- pion or Kir intermediate states. In the baryonic sector we include qqq states below 1 GeV (the N, A, A, and I states are included with their experimental mass), low lying qq excitations as well as contributions from the contact term; for a direct comparison both surface and volume coupling for the nqq and Kqq vertices is used. For a similar bag structure of both baryons and mesons the only essential parameter in the model is the bag radius (the surface thickness enters as a second parameter for a diffuse bag).

*Submitt«d to IUCF Workshop "Quarks in Nuclei", (1983). •Institute for Theoretical Physics, University Erlangen-Ntirnberg, Erlangen, West Germany. tSupported in part by CNPq, FINEP (Brazil) and KFA (W.Germany). -51-

RelativÍ8tic Mean-Field Formulation for Baryonic Systems**

V.E. Herscovitz, M.R. Teodoro and M. Dillig

In the relativistic Dirac equation for a baryon mean field in a closed shell nucleus spin and isospin saturated, in the Hartree-Dirac approximation, the potential V(r) - V (r) + y V (r) can be generated by boson exchange. N- and \-nucleus single-particle states have been analyzed in such a framework. Some E-nuclei narrow states motivated several studies of absorptive, central and spin-orbit potential components. We consider here OBE and TBE contributions to IN interaction; the first ones include o and u> mesons and the second ones TT, p, K, K*, ic and short-range correlations. Including in V (r) and V (r) the real contributions from OBE and TBE, we have W<> - W'> * i'1-'^»0*'T'0<1~>T"0) Im V is calculated in the recoilless production and static limit si- TTBE tuations.

*Proc. IVth Bras. Meet. Part. & Fields, Itatiais, Brazil (1983), 91-94. •Supported in part by CNPq, FINEP (Brasil) and KFA (W.Germany). ••Institute for Theoretical Physics, University Erlangen-Ntirnberg, Erlangen, West Germany.

12 *+ E-Hypernuclear Low-Lying States in _C

M. Dillig , V.E. Herscovitz and M.R. Teodoro

Starting from a one-boson-exchange model for the IN -+ AN conversion, we derive an absorptive central and spin-orbit potential for E hypernuclei. Im- plications for the widths of Z-hypernuclear states and their selectivity to 12 quantum numbers are demonstrated for the 1p state in _C.

*J. Phys. G: Nucl. Phys. JIO (1984) L59-L64. •Supported in part by CNPq, FINEP (Brasil) and KFA (W.Germany). ••Institute for Theoretical Physics, University of Erlangen-NUrnberg, Erlangen, West Germany. -5 2-

Simplified Relativistic Formulation of Short-Range Correlations for Baryonic Interactions*

V.E. Herscovitz, M.R. Teodoro and M. Dillig

Baryon-Baryon interaction is a fundamental ingredient for the understanding of the structure of baryonic systems. In the boson exchange model for N-N interaction, massive vector mesons are responsible for spin-orbit interaction and short-range repulsion. In the current non-relativistic phenomenology short-range correlations (SRC) depend on a quasi universal factor g'(u> » q =0) related to the Landau-Migdal parameter. We formulate a relativistic extension of such SRC and determine its influence on a study of LN interaction addressed to E-Hypernuclei.

*Vth Bras. Workshop Intern. En., Gramado, Brazil (1984). •Institute for Theoretical Physics, University of Erlangen-NUrnberg, Erlangen, West Germany.

Center-of-Mass and Recoil Corrections in Bag Models*

M. Betz

Approximate methods of eliminating spurious center-of-mass motion and taking into account relativistic recoil in bag models are reviewed. The soliton bag model is used as a framework to define a relativistic center-of- mass position operator. A procedure to construct moving soliton bags is described. Applications to the calculation of charge radii, magnetic moments and form factors of the nucleon are discussed, with particular attention paid to the MIT - bag limit.

*Presented at the V Encontro Nacional de Física de Energias Intermediárias, Gramado, RS (1984); to be published in Revista Brasileira de Física. -53-

A Generalized Treatment of Point Canonical Transformations in the Path Integral*

H.O. Girotti and T.J.M. Simões

We investigate non-linear point canonical transformations within the path integral when an arbitrary discrete procedure is used for defining this integral. By working entirely within the functional formalism, we give a complete derivation of the so called additional potential in this general case. We also present an extension of the average method of McLaughlin and Schulman for path integration in curvilinear coordinates.

*Nuovo Cimento 74B (1983) 59-66.

Quantization of Spontaneously Broken Gauge Theories in the Unitary Gauge Through the Dirac Bracket Formalism*

Horacio 0. Girotti and Heinz J. Rothe

We reconsider the quantization of the Higgs model in the unitary gauge using the Dirac bracket quantization procedure. It is found that the structure of some of the equal-time commutators are quite abnormal. It is then shown in a very clear and systematic way that this anomalous structure is closely connected with the well known quartically divergent contribution to the effective Higgs Lagrangian. This contribution has been shown to play an important role in the cancellation of non-renormalizable divergences.

*Nuovo Cimento 73A (1983) 62-68. +Institut für Theoretische Physik, University of Heidelberg, Germany.

Quantization of QED and QCD in a Fully Fixed Temporal Gauge*

H.O. Girotti and K.D. Rothe+

We present the quantization of QED and QCD in a fully fixed temporal gauge. We thereby obtain an unambiguous expression for the free gauge field -54-

propagator which agrees with that of Caracciolo et al.

*To appear in Zeitschrift fUr Physik C. *Institut für Theoretische Physik, University of Heidelberg, Germany.

Operator Quantization of Non Abelian Gauge Theories in a Completely Fixed Axial Gauge

T.J.M. Simões and H.O. Girotti

A consistent quantization of chromodynamics in a completely fixed axial gauge is carried out by using the Dirac bracket quantization procedure. The maui results are: The translation of Dirac brackets into equal-time commutators is possible, without ambiguities, because of the absence of ordering problems. All equal-time commutators are compatible with constraints and gauge conditions holding as strong operator relations. All equal-time commutators are compatible with chromoeleetrie, chromomagnetic and fermionic fields vanishing at spatial infinity. The coloured gauge potentials A ' , A ' and A ' are seen to develop a physically significant, although pure gauge, behavior at x3 » ±°°, as required by the presence of a non-trivial topological content. Poincaré invariance is satisfied without introducing in the Hamiltonian "extra" quantum mechanical potentials. The determinant of the Faddeev-Popov matrix does not depend upon the field variables.

Dynamics of Gauge Systems and Dirac's Conjecture

M.E.V. Costa, H.O. Girotti and T.J.M. Simões

For systems possessing only first class constraints, we rigorously prove that the secondary constraints act as independent generators of gauge transformations (Dirac's conjecture). The proof essentially consists in demonstra- ting that the total and the extended Hamiltonians generate the same cime evolution for the canonical realization, f(q,p), of the gauge invariant quantities. We also discuss the alternative realizations of these quantities. -55-

Effect of the d-f Coulomb Correlation on the Valence Transition of Intermediate Valence Systems

P.M. Mocs and J.R. Iglesias

The d-f Coulomb repulsion, G, is treated by means of a real space decimation procedure on a Bethe lattice. The valence is calculated as a function of the relative position of the f-level with respect to the conduction band. No discontinuous transitions are found.

Real Space Renormalization of an Anderson Impurity in a Linear Chain

Acirete S. Rosa Simões and J.R. Iglesias

The local density of states and the magnetic moment of an Anderson impurity in a linear chain are studied by means of a real space renormalization technique applied to the first- and second-order Green functions. This scaling approach enables to obtain an exact solution of the alloy analogy for the one impurity case. The case of local and nearest neighbour hybridization are studied using other approximations.

Electronic Transport in Amorphous Metals

I. Aveline, M.N. Baibich and Sonia Frota-Pessoa*

In order to shed some light into the field of electronic transport in metallic glasses, we have started a study of the electrical resistivity of these materials. Avoiding the traditional approaches in this subject (Faber- Ziman, Mott, double well models) we have applied a Kubo Greenwood formalism to the (UPS) measured "density of states" for CuZr amorphous alloys with the purpose of testing the Kubo formula. At a later stage, once satisfactory results are obtained from above, we will apply the same method to the calcu- li lated density of states based on the recursion method developed by one of us . As preliminary results we have found that : 1) a model for the velocity dispersion law appearing in the Kubo Greenwood formula must be considered - we are at present testing the model suggested by -56-

Velicky ; 2) on account of our numerical integration method, we can afford the use of an exact energy deviative of the distribution function leading to a more realistic temperature dependence of the resistivity. The results are to be compared to the experimental results obtained for these alloys .

References: 1) Oelhafen P. e£ a^ - Phys. Rev. Lett. 4_3, 1134 (1979). 2) Frota Pessoa S. - to be published in J. Phys. F: Metal Physics. 3) Velicky B. - Phys. Rev. _184_, 614 (1969). 4) Baibich M.N. e£ a\_ - Phys. Rev. B.

*Instituto de Fisica-USP, Brazil.

Contribution of the Torsional Modes to the Equilibrium Distribution of Vibrational States and to the Specific Heat of a Chain Molecule**

J.A. Borges da Costa, C. Scherer, A. Holz+ and J. Naghizadeh*

The torsional modes of a chain molecule were studied recently under the assumption that it has a well defined spatial configuration at any time. We show how the averages over the possible configurations, for a distribution in thermal equilibrium, should be performed in the calculation of the thermo- dynamical properties. Our results show that the mean density of torsional states increases in the low frequency region with increasing temperature. The specific heat behaviour shows a considerable difference from the result obtained in the previous paper, where only the lowest energetic configuration was considered. The consequences of this result with respect to the configurational properties of polymer molecules near the 0 temperature are discussed.

*Z. Naturforsch. 38a (1983) 1285. •Theoretische Physik, UniversitHt des Saarlandes 6600 SaarbrUcken, RFC tWork partly supported by CNPq (Brazil) and DAAD (Germany) through the agreement of Scientific Exchange. -57-

Renormalization and Critical Behavior of the Continuous Potts Model with External Symmetry Breaking*

Mareia C. Bernardes Barbosa, M.A. Gusmão and W.K. Theumann

The renormalization and the critical behavior of the continuum -field theory to illustrate the renormalization-group procedure and to point out important differences with the usual renormalization of a 4 vector -field theory. Regularization with generalized minimal subtraction, to two-loop order, is then applied to the continuum model, in the representation of Priest and Lubensky, with broken quadratic and trilinear symmetry, in two different cases. One, with symmetry breaking that favors ordering along a single "longitudinal" component of the fields and the other with favored "transverse" ordering. In the first one, only the (unstable) Gaussian fixed point is obtained, a result that remains valid to all orders in perturbation theory and which confirms a physical argument suggesting the absence of a phase transition. The second way of breaking the symmetry yields a crossover I to a (p-1)-state symmetric Potts model, with the expected critical exponents n and v, for general p, providing a check on the renormalization-regulation procedure.

•Master Thesis of Marcir C. Bernardes Barbosa, Instituto de Física-UFRGS, Brazil (October 1984).

Effects of Trilinear Symmetry Breaking on the Potts Model Transition of Uniaxially Stressed SrTiO,

José F. Fontanari and W.K. Theumann

It is shown that a break of trilinear symmetry in the continuous version of the three-state Potts model with linear and quadratic symmetry breaking should be relevant for the trigonal to pseudo-tetragonal phase transition in uniaxially stressed SrTiO. along [1+Ó, 1+6, 1-25]. A number of results -58-

obtained from a Landau analysis of the phase diagrams suggest that new experiments are needed for a confrontation with the theory. These results are: a) the critical and tricritical points at which the first order transition ends or where the change to a continuous transition takes place, disappear for * * values of 6 and 6 of opposite sign to that in the absence of trilinear symmetry breaking, b) Universal amplitude ratios between critical and tricritical parameters are obtained in terms of two dimensionless parameters, c) It is shown that the shift of the tricritical off-diagonal stress, 6 , due to trilinear symmetry breaking is large enough to mask the fluctuation corrections to the ratio 6/6 calculated by Blankschtein and Aharony to order with the renormalization group in d • 4-e dimensions.

Real Space Renormalization Group and Electron Localization in Random Potentials

Alba Theumann

The conductivity of electrons in random potentials is studied for dimen- sionalities d- 1 and d » 2 by means of decimation and the method of Migdal- Kadanoff. In the case of the linear chain we obtained renormalization group (R.G.) recursion relations for the probability distributions of the random potentials. It was possible to find a non-trivial analitic solution to the integral equation in the form of a family of probability distributions that transform among themselves under the operation of the R.G.. The calculation of the conductivity shows an exponential decrease with the length of the chain, a result already established by other methods. It is presently under work the study of the two-dimensional system by analyzing the recursion relations obtained in the Migdal-Kadanoff scheme.

Quantum Spin Glass. A Replica Symmetric Theory with Positive Entropy*

Alba Theuman

In the present work it is presented a detailed analysis of quantum effects in the spin glass transition as described by a quantum Heisenberg analogue of S.K. model. The spin operators are represented in terms of two -59-

fermioii levels at one site in a random time dependent field and with an interaction delocalized in time. It is shown that within a Hartree-Fock approximation in a replica symmetric theory one obtains a mean field description of the transition with satisfactory zero temperature properties. The transition is described by two order parameters, one of them being the static magnetic susceptibility and the other the S.G. order parameter. The saddle point equations obtained in this work are analogous to those of Sommers for a theory of classical spins.

*Supported by CNPq and FINEP, Brazil.

Second-Quantized Theory of Anderson Localization in d = 2»e*

Alba Theumann

Renormalized perturbation-theory methods with dimensional regularization «ve applied to th^- localization transition of electrons in random potentials within a field theory where the generating functional is the configurational averagvd (Z ) for Z the vacuum-to-vacuum amplitude expressed as a functional integral over Grassman fields, in the replica limit n = 0. The bare parameters of the theory ire the Fermi level E and the variance of the random potential W . Power counting says that at dimensionality d = 2+e the theory is super- renormalizable. Renormalization of the inverse propagator by the definition of renormalized Fermi level and interaction, E and u = (nW /EL)k ~ , respectively, in order to cancel the single dimensional pole, leads to the same Wilson function 6(u) as for the compact nonlinear o model when the scale parameter k is varied at constant W /E . The conductivity is calculated in a -1 ° -1 d/2-1 perturbation expansion in (TE_) , with T » nW E. being the inverse lifetime, at d - 2+e. It is explicitly shown that in ultraviolet-divergent d-dimensional loop integrals over advanced and retarded'propagators, the leading term is regular while the dimensional pole occurs in the next-to- leading term. Then to leading order the conductivity o (u>) is regular while o the first correction that includes the diffusion modes has a dimensional pole 2 e/2 with residue %(iui/k ) . To cancel this pole a renormalized inverse conduc- tance t(u) is defined, and the new Wilson function B(t) obtained by varying k at constant "bare" interaction W /&_ coincides with the scaling theory of -60-

Abrahams, Anderson, Licciardello, and Ramakrishnan. Scaling laws are derived from the solution of the renormalization-group equation for the conductivity.

Phys. Rev. B 28 (1983) 6453.

Singularities in the Pararoagnetism of Two-Dimensional Nearly Magnetic Itinerant-Fermion Systems at very low Temperature: Application to Degenerate Two-PTwo-Dimensionai l Liquid- He Films*

A. Theumann and M.T.Beal-Monod+

It is shown that two-dimensional (2D) paramagnon problems exhibit strong algebraic singularities |q -41^ |~ , when some relevant momentum q is close to twice the Fermi momentum K_,. As all q values from 0 to 2K_ are equally relevant for the magnetic instability in 2D, the above singularities play a key role. By contrast, they are irrelevant in 3D. It is explicitly shown that standard methods to calculate the uniform static susceptibility fail in 2D due to these singular terms. The origin of the singularities are multitail ring diagrams, closed fermion loops with "tails" attached to them. These diagrams are analyzed in detail by generalizing to d dimensions and dynamic tails, the method of Brovman and Kagan, developed in another context. The subsequent effects in the Ginzburg-Landau-Wilson Lagrangian describing interacting paramagnons are dramatic and render such an expansion questionable. Moreover, the nature of the magnetic instability (ferromagnetic or antiferromagnetic type), which is not well defined in mean-field theory, still remains unsolved in the presence of paramagnons since standard methods to renormalize the response functions with fluctuations fail to apply in the 2D problem. Any naive trans- position from 3D to 9D of the Landau Fermi-liquid theory to compute, for 3 instance, properties of lliquidi - He films are suspected to be premature - if not erroneous - at this stage.

*Phys. Rev. B 29 (1984) 2567. •Laboratoire de Physique des Solides associe au Centre National de la Recherche Scientifique, Université de Paris-Sud, F-91405 Orsay, France. -61- í t i *s 'i | Quantum Ising Spin-Glass* I Alba Theumann+ and Mercedes Vieira Gusmão

I A random, quantum model of interacting spins, where the spin operators I are represented by bilinear combinations of fermions, is studied in the Ising I : limit and in the static approximation. Assuming replica symmetry we recover basically the results of Sherrington and Kirkpatric. Effects of quantum fluctuations remain in the determination of the static susceptibility x as an independent order parameter and the breakdown of the Fischer relation. *Phys. Letters 105A (1984) 311. • -«-Supported by Financiadora de Estudos e Projetos (FINEP) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Brazil.

Critical Exponents for $ -Field Models with Long-Range Interactions*

W.K. Theumann and M.A. Gusmão

The critical exponents for two $ -field theories with long-range (LR) interactions decaying as 1/R ° , o > 0, are calculated to two-loop order in renonnalized perturbation theory in d < 3o-e' dimensions. One is the continuum version of the p-state Potts model and the other is the scalar field theory with imaginary coupling that describes the Yang-Lee edge-singularity problem. The two crossover exponents for quadratic symmetry breaking discussed by Wallace and Young and in recent work by the present authors are also calculated in the first case. By means of renormalization-group recursion relations to one-loop order, it is shown that the LR fixed point is stable for all a < 2 whenever n-»» the critical correlation-function exponent for short-range (SR) interactions, is negative, implying a discontinuity of critical exponents at o - 2. This is the case for the (p < 2)-state Potts model and for the Yang-Lee edge-singularity problem, and is in agreement with recent results by Chang and Sak for the Ising spin-glass problem. For the (p > 2)-state Potts model there

is an indication of a continuous crossover to SR behavior at o - 2-nco, with

ngR > 0. It is pointed out that a number of exact results [B - (1-e'/2o ov, dm (d-o)/(d+cO, in which 5 is the Yang-Lee edge-singularity exponent and -62-

j~ x (d-o)/2 may apply within the LR expansion depending on n = 2-o (shown here to hold at least to two-loop order) being exact, to all orders.

*To be published in Phys. Rev. B. 31 (1985).

Crossover from First-Order and Near-Spinodal First-Order to Continuous Transitions in the Three- and Four-State Potts Model*

W.K. Theumann

A calculation in renormalized perturbation theory, to one-loop order, in d * 6-e dimensions, shows that quadratic-symmetry breaking (QSB) in a continuum-field p-state Potts model yields a further distinction between the usual first-order and a "near-spinodal first-order" transition with a metastable state. Whereas the latter can cross over to a continuous transition at a tricritical point with arbitrarily small but finite QSB, the former one requires a QSB above a threshold value. Specific results for the three- and four-state Potts model suggest that this could be used to distinguish experimentally between the two first-order transitions.

*Phys. Rev. B 28 (1983) 6519.

Validity of the Long-Range Expansion in the n-Vector Model*

M.A. Gusmão and W.K. Theumann

The critical behavior of an n-component system in d dimensions with long- range (LR) interactions decaying as 1/|r| +0, for a > 0, is reexamined near the crossover to short-range (SR) behavior, where o = 2, by means of renormalized perturbation theory in e' - 2o-d. It is pointed out that 2-o should not be viewed as an expansion parameter, and consequently the critical exponents turn out to be discontinuous at o • 2 without the intermediate region of weakly LR interactions fourM earlier by Sak. For any o < 2 it is shown that (i) the LR expansion is stable to weak SR perturbation and (ii) the SR expansion in c > 4-d breaks down under a weak LR perturbation.

*Phys. Rev. B 28 (1983) 6545. -63-

Crossover Exponents for the Potts Model with Quadratic Symmetry Breaking*

W.K. Theumann and M.A. Gusmão

The effect of quadratic symmetry breaking (QSB) on two representations for the Potts vectors in a continuum-field model are studied to two-loop order in renormalized perturbation theory in d = 6-e dimensions, in extension of an earlier group-theoretical analysis by Wallace and Young. The explicit dependence of the crossover exponent that corresponds to QSB that destroys the equivalence between pairs of Potts vectors is obtained as a function of d and n for the p-state uiodel with p = n+1. It is shown that this exponent follows from the calculation of vertex functions in a representation due to Wallace and Young, whereas a second crossover exponent $•, that can be identified with the critical exponent 6, and which corresponds to QSB that favors a single Potts vector against the others, follows from a calculation using the representation of the Potts vectors due to Priest and Lubensky.

*Phys. Rev. B 30 (1984) 2800.

First-Order Phase Transitions in the Potts Model with Trilinear Symmetry Breaking*

W.K. Theumann

It is shown that a trilinear symmetry breaking which destroys the equivalence of the states in a continuum generalization of the p-state Potts model yields first-order phase transitions for all p > 1, in contrast to the results of the symmetric theory where there is a second-order transition for p < 2 and a first-order transition for p > 2, in d * 6-e dimensions, and in spite of mean-field - theory predictions. A calculation in renormalized perturbation theory, to one-loop order, on a three-trilinear-coupling theory yields two new accessible and partly stable asymmetric fixed points beyond the symmetric one, except for the three-state Potts model, one for 2.2"

-*-, which are interpreted as the usual first-order transitions. For the indicated ranges of p the transitions are of first order I -64-

near a spinodal point, with uniaxial ordering in the first case and transverse ordering in the second. Critical exponents that could describe the approach to the spinodal points are explicitly calculated.

*Phys. Rev. B 27 (1983) 6941.

Effect of the Coulomb Repulsion Between Localized and Itinerant Electrons in the Anderson Hamiltonian*

I. Aveline and J.R. Iglesias

The Anderson hamiltonian has been used by several authors to determine in which conditions the Kondo and intermediate valence behaviour set up. In the present work, we have included a term in the Anderson hamiltonian that takes into account the Coulomb repulsion between conduction (d) and localized 2) (f) electrons. This is the G-term of the Ramirez-Falicov-Kamball model, which has been used to explain the valence transition in mixed valence materials. We have shown that the inclusion of the G term and the use of a simple decoupling procedure for the Green functions, in the limit of high temperatures, leads to the following conclusions: a) the position of the impurity level E is pushed slightly towards the Fermi level, and b) the temperature dependence of E reproduces very well preceding results , without the need of sofisticated decoupling schemes.

1) Lacroix, C, J. Phys. F: Metal Physics 11, 2389 (1981). 2) Ramirez, R., Falicov, L, Kimball, J.C., Phys. Rev. B,2, 3383 (1970).

*Paper presented at Annual Meeting of the Brazilian Physical Society, São Paulo, SP, Brazil, July 1984. Abstract in Supl. of Ciência e Cultura, 36, 330 (1984). ~~ -65-

The Liquid Metal Models Applied to Glassy Metals**

Mario N. Baibich

A review of the theory for electronic transport in liquid metals such as is extended to amorphous metals is presented. We obtain expressions for the resistivity and thermopower for simple metals and alloys according to a Faber-Ziman calculation. The suitability of different approaches to the calculation of the parameters is discussed for different compositions. A simplified, "lab-oriented", Faber Ziman formulation is presented as well as a discussion of consistency of results for changing compositions. The cross term is shown to be the most important contribution, containing scattering from unlike pairs.

*Work partially supported by CNPq, FINEP, PROPESP-UFRGS, Brazil. +To appear in the Annals of I Simpósio Latino-Americano de Física dos Siste- mas Amorfos, Niterói, RJ, 1984. Supplement to Revista Brasileira de Física.

Kondo-Type Theories Applied to Amorphous Metals**

Mario N. Baibich

The Kondo type theories used to explain the electrical resistivity of amorphous metals at low temperatures are reviewed. A simple introduction to the traditional Kondo effect is presented to serve as a base for the discussion of the proposed theories for glassy metals. We present the modified (magnetic) Kondo effect and the structural equivalent of it along with a study of predicted behaviour compared to experimental results.

*Work supported in part by CNPq, FINEP, PROPESP-UFRGS, Brazil •To be published in the Annals of I Simpósio Latino-Americano de Física dos Sistemas Amorfos, Niterói, RJ, 1984. Supplement to Revista Brasileira de Física. -66-

Metallic Glass Formation*'*'

Mario N. Baibich

In this article we present some of the most used empirical rules and the essence of Che proposed theories to explain the obtention or not of amorphous metals. We treat the final (amorphous) metastable state, the kinetics of glass formation and some Laboratory Rules such as the ratio of atomic sizes, valence electrons and density of states, competition of complex phases, the "anti- stable intermetallic" and polimorphism. We also show the ideas involved in a "ab initio" calculation and thermodynamic variational methods of calculation.

*Work supported in part by CNPq, FINEP, PROPESP-UFRGS, Brazil. +To appear in the Annals of I Simpósio Latino-Americano de Física dos Sistemas Amorfos, Niterói, RJ, 1984. Supplement to Revista Brasileira de Física.

A New Approximation for the RFK Model*

Nelson Porras Montenegro, I. Aveline and J.R. Iglesias

The Coulomb repulsion G between localized and conduction electrons, introduced by Ramirez-Falicov and Kimball theory for intermediate valence systems has been treated in a new approximation. A discontinuous transition was found, but no fractional occupation of the localized states although an hybridization term was included.

1) Ramirez, R.; Falicov, L.M. and Kimball, J.C.; Phys. Rev. B 2, 3383 (1970)

•Published in Rev. Bras, de Física, V3, n9 1, (1983) 39.

Effect of the Spatial Correlation on the Alloy Analogy Solution of the Hubbard Hamiltonian

P.M. Mors, E.V. Anda* and J.R. Iglesias

The alloy analogy solution of the Hubbard Hamiltonian describes the system as if there is no correlation between sites. Here, it is shown that the correct description is that of a correlated alloy. Taking into account just -67-

two-sites correlation, we obtain a different shape for the density of states and a more restrictive criterium for the metal-insulator transition.

*Instituto de Física, Universidade Federal Fluminense, 24210 Niterói, RJ, Brazil.

A Diagrammatic Method for a Mixed Valence Hamiltonian*

A.S. da Rosa Simões and J.R. Iglesias

An approximate diagrammatic method is utilized to calculate the valence and densities of states of a two band system with inter-and intra-band Coulomb interactions at T « 0 K. The results indicate the existence of an intermediate valence state and a metal-insulator transition that can.be continuous or discontinuous depending on the ratio G/V; G is the inter-band Coulomb repulsion and W the conduction band half-width.

*J. of Magnetism and Magnetic Materials 31-34 (1983) 471.

Effect of d-f Correlation on the Electronic Structure of Intermediate Valence Systems

J.R. Iglesias, P. M. Mors and J. Flouquet+

The electronic structure of an intermediate valence system is calculated by means of a real space renorraalization technique on a Bethe lattice. The d-f Coulomb repulsion G is included and treated into the alloy-analogy approximation. The valence and the densities of states are calculated as a function of G. We find that the number of f-electrons increases and the hybridization gap decreases when G increases.

•Centre de Recherches sur les Três Basses Temperatures, CNRS, BP 166 X, 38042 Grenoble, France. -68-

Green-Function Method for a Mixed-Valence Hamiltonian*

Acirete S. Rosa Simões, J.R. Iglesias and E.V. Anda+

A Green-function diagrammatic method is utilized to calculate the occupation number of a narrow (f) band in a mixed-valence system. The method is a generalization of the Hubbard-I approximation for a two-band Hamiltonian. The results at T • 0 K indicate the existence of an intermediate-valence state for finite hybridization between the bands, and abrupt transitions for values of G comparable to the half bandwidth of the conduction band. A metal-insulator transition is also obtained.

*Phys. Rev. B 29 (198') 3085. •Instituto de ITsica, Universidade Federal Fluminense, 24000 Niterói, RJ, Brazil.

Binding Energy of a Hydrogen Impurity in an f.c.c. Lattice*

Andrea Latge, Rejane M. Ribeiro-Teixeira and J.R. Iglesias

Hydrogen impurities in f.c.c. lattices, Pd metal for example, can occupy two interstitial sites, with tetrahedral or octahedral symmetries. Using the Husimi cactus to represent the f.c.c. lattice and two clusters to describe the two different interstices, we calculate the densities of states and the occupation numbers at the impurity site and on its nearest neighbours. The binding energies are calculated and plotted against the hopping integral between the hydrogen and its neighbours (t ). We found that the octahedral site is the stable one for values of t from 0 to 1.5 eV.

*Solid State Comm. 52 (1984) 87.

Real Space Renormalization of a Mixed Valence Hamiltonian on a Bethe Lattice

P.M. Mors, Acirete S. Rosa Simões, J.R. Iglesias and E.V. Anda*

A mixed valence system may be described by two hybridized bands: a narrow one with strong Coulomb interaction and a conduction band. We study this model -69-

I by means of a decimation method originally developed for a linear chain and I recently extended to a Bethe lattice. Different values of the hybridization í I are compared. The densities of states so obtained exhibit a more detailed i I structure than equivalent CPA calculations.

• *Instituto de Física, Univ. Federal Fluminense, 24210 Niterói, RJ, Brazil. -70-

Wave Absorption by Fast Electrons with Non-Maxwellian Perpendicular Momentum Distributions*

L.F. Ziebell and D. Dillenburg

The problem of simultaneous lower hybrid and electron cyclotron plasma heating is considered. It is shown that the shape of the perpendicular momentum distribution of the fast electrons (generated by lower hybrid waves) may strongly modify the absorption spectrum of the electron cyclotron waves.

*IV Japan-Brazil Symposium on Science and Technology, Vol. Ill, Energy-Nuclear Fusion, pg. 150-161, Academia de Ciências do Estado de S.Paulo, 1984.

Effect of Electron Thermal Anisotropy on the Kinetic Cross-Field Streaming Instability*

S.T. Tsai+, M. Tanaka+, J.D. Gaffey, Jr. + , C.S. Wu+, E.H.da Jornada and L.F. Ziebell

The investigation of the kinetic cross-field streaming instability, motivated by the research of collisionless shock waves and previously studied by Wu et al, is discussed more fully in the present work. Since, in the ramp region of a quasi-perpendicular shock, electrons can be preferentially heated in the direction transverse to the ambient magnetic field, it is both desirable and necessary to include the effect of the thermal anisotropy on the instability associated with a shock. The present study has found that T > T can significantly enhance the peak growth rate of the cross-field streaming instability when the electron beta is sufficiently high. Furthermore, the present analysis also improves the analytical and numerical solutions previously obtained.

*J. Plasma Physics _32 (1984) 159. ••-Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742. -71-

Excitation of Whistler Waves by Reflected Auroral Electrons*

C.S. Wu+, D.Dillenburg, L.F. Ziebell and H.P. Freund

Excitation of electron cyclotron waves and whistlers by reflected auroral electron which possess a loss-cone distribution is investigated. Based on a given magnetic field and density model, the instability problem is studied over a broad region along the auroral field lines. This region covers altitudes ranging from one quarter of an Earth radius to five Earth radii. It is found that the growth rate is significant only in the region of low altitude, say below the source region of the auroral kilometric radiation. In the high altitude region the instability is insignificant either because of low refractive indices or because of small loss cone angles.

*Planet Space Sci. Vol. 31, N9 5 (1983) 499. +lnstitute for Physical Science and Technology, University of Maryland, College Park, MD 20742, USA. ++Science Applications, Inc. McLean, VA 22102, USA.

Momentum Distribution Dependence of Induced Electron-Cyclotron Emission*

L.F. Ziebell and D. Dillenburg

The dependence of the electron-cyclotron wave amplification in an inhomogeneous plasma slab on the electron momentum distribution is investigated. Two types of distributions are considered, both featuring a loss cone and a Maxwellian component. It is shown that the perpendicular emission at the fundament 1 frequency is in general greatly reduced by the presence of a Maxwellian component and situations occur in which a layer in the slab very effectively absorbs all the radiation amplified elsewhere. The transition from the pure loss cone to the pure Maxwellian case is accompanied by a peculiar behavior of the dielectric tensor components, which may invalidate the ge- ometrical optics approximation in the calculation of the emission and the commonly held belief that the real part of the refractive index is insensitive to the shape of the momentum distribution function.

*Revista Brasileira de Física, Vol. 13, n9 4, 1983. -72-

Angular and Momentum Distribution Dependence of Electron Cyclotron Absorption and Amplification in Mirror-Confined Plasmas

L.F. Ziebell

The absorption and amplification of fundamental electron cyclotron radiation in inhomogeneous, weakly relativistic, loss-cone and partially filled loss-cone plasmas, are studied for both perpendicular and oblique propagation, and the extraordinary mode is numerically analyzed. It is shown that there are situations where small changes in the distribution function may strongly affect the wave vector, and an explanation is given, pointing to the eventual relevance of the use of the full momentum distribution, along with relativistic effects, in the evaluation of both the real and imaginary part of the dielectric tensor. A model which could describe plasmas in actual situations like the thermal barriers in tandem mirror devices is presented and numerically investigated, and it is shown that particles scattered into the loss-cone may play a relevant role.

Instabilities Excited by an Energetic Ion Beam and Electronic Temperature Anisotropy in Tandem Mirrors*

E.H.da Jornada , J.D. Gaffey, Jr., and D. Winske Institute for Physical Science and Technology, university of Maryland, College Park, MD 20742, USA

The theory of cross-field ion streaming instabilities is applied to the parameter regime of the end cells of the upgraded Tandem Mirror Experiment with neutral beam injection. The cross-field ion drift as well as the electron thermal anisotropy T > T provides the free-energy which drives various instabilities. Three instabilities, a nearly perpendicular propagating modified two-stream instability, an obliquely propagating ion-ion streaming instability, and an obliquely propagating electromagnetic lower-hybrid instability, have been identified. The first two waves are electrostatic and have the largest growth rate. For the actual operation conditions of the Tandem Mirror machines, it is found nhat the ion-ion streaming instability has the largest growth rate. When more energetic neutral beams become -73-

available, the two-stream instability may play the dominant role in the instability of these devices.

*Accepted for publication in Physics of Fluids. •On leave from IF-UFRGS, Brazil. ++Los Alamos National Laboratory, X-1, MS E-531, Los Alamos, NM 87545, USA

Instabilities Due to Transmitted and Reflected Ions and Electron Temperature Anisotropy in a Quasiperpendicular Shock Wave J.D. Gaffey, Jr., E.H.da Jornada*, C.S. Wu, and D. Winske+ Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742, USA

The theory of cross-field ion streaming instabilities is generalized to treat two ion species, transmitted and reflected, and applied to the parameter regime of a high Mach number quasiperpendicular shock wave. Electron temperature anisotropy is also included in the analysis because the electrons are preferentially heated in the direction transverse to the ambient magnetic field by adiabatic compression at the shock surface. Improved analytical and numerical results for the linear growth rates are presented. Three modes are discussed: a nearly perpendicular propagating kinetic cross-field streaming instability, an obliquely propagating electromagnetic lower-hybrid instability and a nearly parallel propagating whistler instability. The free energy which drives the instabilities is provided by the cross-field ion drift and the electron temperature anisotropy T > T . The kinetic cross-field streaming ex eii instability is excited by the cross-field ion drift and enhanced by increasing the electron temperature anisotropy. The electromagnetic lower-hybrid instability requires T > T and is enhanced by increasing the ion drift velocity. The nearly parallel propagating whistler instability is excited by T > T and is insensitive to the ion drift. *0n leave from IF-UFRGS, Brazil. •••Los Alamos National Laboratory, S-1, MS E-531, Los Alamos, NM 87545, USA. -74-

Induced Electron-Cyclotron Emission from Inhomogeneous, Anisotropic Plasmas with Electron Population Inversion*

L.F. Ziebell and D. Dillenburg

The amplified emission of electron cyclotron radiation near the fundamental frequency from an inhomogeneous, anisotropic plasma slab with a loss-cone-type electron velocity distribution, is investigated in a linear theory. Plasma polarization effects are consistently included. Expressions are developed in the WKB approximation for emission in the ordinary and the extraordinary modes, for propagation perpendicular to the magnetic field. Numerical results are given for the extraordinary mode, for which effects are strongest. It is shown that the amplification is sensitively dependent on the ratio of parallel-to-perpendicular temperature and on inhomogeneities in the magnetic field.

*Phys. of Fluids 26 (1983) 80.

Dissipative Instabilities in the Edge of Reversed-Field Pinches Driven by a Combination of Plasma Gradients and a Parallel Current*

J.P. Mondt* and J. Goedert8

Stability in the edge region of reversed-field pinches is analyzed within the context of a two-fluid model. Two major sources of instability are identified: in combination with a parallel electric field, either an electron temperature gradient and/or a density gradient leads to rapid growth (of several to many ohmic heating rates) over a region of several mm around the mode-rational surfaces in the edge region. The basic signature of both instabilities is electrostatic. In the case of the density gradient mode, it relies bn the effects of electron compressibility, whereas the temperature gradient mode can be identified as the current-convective instability by Caking the limit of zero density gradient, thermal force, and electron compressibility. The possibility of enhanced particle loss and thermal convection as a nonlinear consequence of the instability is indicated. A criterion for the overlap of the linearly unstable regions in the edge of -75-

reversed-field pinches is obtained.

*To be published in Physics of Fluids. +Los Alamos National Laboratory, Los Alamos, NM 87545, USA. 5On leave from IF-UFRGS, Brazil.

Exact Solutions of the Time-Dependent Vlasov Equations* + § Joao Goedert and H.Ralph Lewis

In this paper we describe our use of a momentum resonance ansatz of Lewis and Leach to study exact invariants for time-dependent one-dimensional potentials. This ansatz provides a framework for finding invariants admitted by a larger class of time-dependent potentials than was known previously. For a potential that admits an exact invariant in this resonance form, we have shown how to construct the invariant as a functional of the potential in terms of the solution of a definite linear algebraic system of equations. We have found a necessary and sufficient condition on the potential for the existence of an invariant with a given number of resonances. There exist more potentials that admit invariants with two resonances than were previously known and we have found an example in parametric form of such a potential. We have also found examples of potentials that admit invariants with three resonances.

*Bull. Am. Phys. Soc. 29 (1984) 1241. §Los Alamos National Laboratory •On leave from IF-UFRGS, Brazil.

Thermal Instabilities in the Edge Region of Reversed-Field Pinches*

J. Goedert* and J.P. Mondt**

Due to high current and relatively low temperature, ohmic heating rates are fast enough to drive thermal instabilities in the edge region of Reversed- Field Pinches, on time scales of several tens of microseconds or less. For low beta an eigenvalue equation for cylindrical geometry is obtained. For the most interesting case of high mode numbers (hence small inductive effects) a cubic dispersion equation results, portending instability over a wide parameter -76-

range. In the physically interesting case when the parallel electron drift frequency is small compared with the ohmic heating rate, the radial extent of the unstable region around the field reversal layer is derived.

*Los Alamos National Laboratory Document LA-10029MS, Los Alamos, April 1984. +0n leave from Instituto de FÍsica-UFRGS, Brazil.

The Effect of Thermal Processes on Stability in the Edge of Reversed-Field Pinches*

J.P. Mondt+ and J. Goedert++

Thermal stability of the edge region of reversed-fiald pinches is analyzed within the context of a two-flifd model . Two major sources of excit- ? If ation are identified" that are operative in combination with a parallel electric field: either an electron twnperature gradient and/or a density gradient Leading to rapid growth (serrai to ma«y Ohmic. heating rates). The basic signature of both instabilities-"^ electrostatic. In the case of the instability driven by a density gradient electrqji compressibility is essential, whereas the temperature gradient instability ian be identified as the current- convective instability in the limit of zero aiamagnetic drift, density gradient, thermal force, drift heat flux, and election compressibility. The results of the present work indicatemhe possibility of enhanced thermal convection in the edge as a consequence of high parallel current densities there. The importance of thermal processes as a source of instability in the cold plasma edge is emphasized. 1. S.I.Braginskii, in Reviews of Plasma Physics (Consultants Bureau, New York, 1965), vol. 1, p. 205. 2. J.Goedert and J.P.Mondt, "Thermal Instabilities in the Edge Region of Re- versed-Field Pinches", Los Alamos National Laboratory Document LA-10029-MS, Los Alamos, April 1984. 3. 3.B.Xadomtsev and O.P.Pogutse, in Reviews of Plasma Physics (Consultants Bureau, New York, 1970), Vol. 5, pp. 249-400.

•«•Los Alamos National Laboratory, Los Alamos, New Mexico, USA. ++0n leave from Instituto de FÍsica-UFRGS, Brazil. *Bull. Am. Phys. Soc. 29 (1984) 1356. -77-

Exact Invariants in the Form of Momentum Resonances for Particle Motion in One-Dimensional, Time-Dependent Potentials*

João Goedert and H. Ralph Lewis

We have used the ressonance ansatz of Lewis and Leach to study the structure of explicitly time-dependent, one-dimensional potentials for which exact invariants can be found. For a potential which admits an exact invariant in resonance form, we have shown how to construct the invariant in terms of the solution of a definite linear algebraic system of equations; the invariant is expressed explicitly as a function of the potential. We have shown that there exist new potentials which admit invariants with two resonances and we have found an example in parametric form of such a potential. We have also found an example of a time-dependent potencial that admits an invariant with three resonances. We have shown how to express any invariant of the resonance type explicitly in terms of the moments g and quantities that are obtained as the solution of a definite linear algebraic system of equations. We have used insight gained from tht- moment formulation to find a necess- sary and sufficient condition that characterizes all potentials that admit an invariant with two poles. We have shown that there exists a wider class of potentials that admit an invariant with two poles than had been found previously and we have obtained an example of one of the new potentials. We have not studied the three resonance case in detail. However, in a cursory preliminary study, we have found an example of a potential that admits an invariant with three resonances.

*Proceedings of the "Workshop on Methods of Nonlinear Dynamics", Naval Surface Weapons Center, Dept. of the Navy, Washington, DC (to be published by Sprin- ger-Verlag). +0n leave from Instituto de Física-UFRCS, Brazil. •M-LOS Alamos National Laboratory, MS-F642, Los Alamos, New Mexico 87545, USA. ASTRONOMY AND ASTROPHYSICS -79-

Spectrophotometry of the Nucleus of NGC 7552*

Horacio Dottori, Miriani Pastoriza, Sayd Codina Landaberry , José de Freitas Pacheco

In this paper we present new spectrophotometry measurements of the Sersic-Pastoriza nucleus of NGC7552, giving absolute fluxes of the continuum between 365O& and 6900Ã and intensities of the lines H2, Hg, |oill| 4959+50078 and Ha+NII. The synthesis of the absorption spectrum indicates 3 or 4 burst of star formation.

*Proceeding of the 4th Latin American Regional Meeting of the IAU, Editor José Pacheco, Rio de Janeiro, 1984. •Observatório Nacional, CNPq, Brazil.

Age Determination of HII Regions of the LMC and SMC*

M.V. Copetti, H.A. Dottori, E.L. Bica, M.G. Pastoriza

HII region models were constructed which take into account: 19) A burst for the formation of the ionizing association; 29) Different Salpeter's initial mass function (1 Sx- 3) and upper stellar mass limit (30 S M /M £ 120); 39) Models of stellar evolution with and without mass loss.

*S. van den Bergh and K.S. de Boer (eds.), Structure and Evolution of the Magellanic Clouds, 383-384, IAU Symposium 108.

Burst of Star Formation in Detached Extragalactic HII Regions: A Qualitative Analysis*

Horacio A. Dottori

A calibration previously determined for the evolution of the equivalent width of the emission line HB with age for HII regions is applied to detached extragalactic HII regions. The frequency distribution of ages seems to indicate that some of these regions had other bursts of star formation so important as the observed last one.

«Astrophysics and Space Science 90 (1983) 385. -80-

A Study about the Existence of Periodic Components in the U, B, V Variability of Seyfert Nuclei

S.M. Bisch*, M.G. Pastoriza, H. Dottori, I. Busko*

We analysed Penfold's (1979) U, B, V observations of the nuclei of 7 Seyfert galaxies: NGC 1566, NGC 3227, NGC 3783, 1C 4329A, Mk 50, NGC 6814 and NGC 7469, with a 14,3" apperture, looking for a possible periodicity in the variations shown in the three bands and U-B, B-V color indices. A generalization of the method of the Date Compensated Fourier Transform (DCDFT), proposed by Ferraz Mello (1977, 1981), adequate to the analysis of observations unequally spaced in time and based on the fitting of periodic 2 functions and the calculation of the multiple correlation coefficient R was developed to analyse the data. One of the 7 galaxies analysed (NGC 1566) shows a very small variation amplitude, not allowing any conclusions. All the others analysed revealed a high probability of having a periodic component in the variations. In Mk 50 the component is unique, whereas in the other 5 two components were detected: a fast one and a slow one. The periodicity of the slow being rather uncertain due to the fact that the estimated periods are bigger or equal to the total time interval covered by the analysed observations. For the fast component there is a clear tendency to periodic repetition, but with possible variations in phase and amplitude. The periods and the amplitudes of the two components seem to keep a certain proportion: P s 10P2 and A s 1,7( 0.3)A2, where 1 denotes the slow component and 2 the fast one. A correlation between the variation amplitudes and the real diameter, in parsecs, of the nuclear region in the 14,3" apperture was also found: the amplitude increases toward smaller diameter. Recent observations of NGC 6814 and NGC 7469 done at the Observatório Astrofísico Brasileiro (OAB) were used to test the estimates of their slow components. For NGC 6814 it was not confirmed whereas for NGC 7469 it remains valid. In the table are listed the principal results and the figures illustrate the Penfold's observations and fitted sinusoids.

Penfold, J.E, 1979, Mont. Not. R. Astr. Soc, _186_, 297. Ferraz Mello, S., 1977, in Colóquio sobre Estrelas Binárias, edited by R. Vilhena de Moraes (Sociedade Astronômica Brasileira, São Paulo), p. 277. -81-

Ferraz Mello, S., 1981, Astron. J., 86 (4), 619.

*Dept. de Física e Química, UFES. -«•Observatório Nacional, CNPq.

Table

Peri ods AMPLITUDE Or THE VARIATION (day) AU AB AV A(U-B) A(B-V) ÍGC 3227 1000 0,81 - - 0,47 - 150 0,47 0,24

IGC 3783 750 0,43 0,27 - - 50 0,25 0,17 -

IC 4329A > 1000 1,64 4,23 0,29 500 0,27 0,19 0,16 - -

Mk 50 450 1,18 0,48 0,28 0,74 0,23

v ; ;;GC 6814 870 0,75 ,,, - 0.49 n* - 1 ; ; 75 0,45(±0,28) - 0,26(+0,16r

::GC 746S > 1000 0,32 1,04 125 0,23 0,17 - - - "I" 1 1 —I— —1 f— 1 1 i 1 1 r~—i—ii -

-0.2 I a 1 *— T I • ^ U-B 0.0 a 0.0001 0.2

0.4 1 ! i 1 I } l iiii i i i 2200 C300 2 kOO 2500 2600 2700 2800 2900 - 1 1 1 1 1 I 1 1 1 1 1 13.6 - I I - —^ 13.^. I ^—— u 0.0002 14.2 - I

14.4 -

14.6 / 1 1 1 1 1 1 1 1 1 1 1 i i 1 1 2200 2300 2<»00 2500 2600 2700 2800 2900

Fig. IV-6. NGC 3227, fitting at lone; period

U-B

2200 2100 21.00 2SO0 26 00 2700 2600 2900 I IIII l IIII 1 l 13.6 - 1/ - r\ /~\ 13.8 - INI -

14.0 - 1 U r 14.2 - v 14.4 " \ J / 14.6 1 IIII 1 1 1 IIII 1 1 2200 2S00 2*00 2S00 2600 2700 2*00 2900

Fig. IV-7. NGC 3227, simultaneous fitting at periods cf lOOOd and 150d. -83-

1 1 1 1 1 1 1 1 1 I I I I 1 i 13.0 - I 13.2 - • i X —— " •—x. -J ., V * l~—- I * —• •^—— 1 —r 1 13.4 — 1 0.0012 I I 1 13.5 1 1 1 1 1 1 1 , i i i i I i i 2200 2300 2"»00 2500 2600 2700 2600 2900 3O00

13.6-

B 13.8 0.0013 14.0

14.2 I I I I I I I I I I I I I I I 2200 2300 2U00 2S00 2600 2700 2800 2900 3000 1 1 1 i i i 1 1 1 1 1 1 1 1 1 12.8 -

13.0 I • 13.2 i T _^- -* —^ u : «^^^^ ^ . i i ^—• I 0.0014 13.4 ~—-—i -i I I i i 13.6 i i i i i i | 1 1 1 1 1 1 | | 2200 2300 2W00 2500 2600 2700 2800 2900 3000

Fig» IV-18. NGC 3783, fitting at long period -84-

i i i i i i i i i i 11111 1 ' 13.6 - V 1— ^-^_-Jr— ^——•i-* \ 0.0006 13.8 - 0.0021 14.0 -

i I I I i I i i i i i i i i i

2200 2300 2<)00 2S0O 2600 2700 2S00 2900 3000 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 14 .6

14.8 ? B ^T" " -^«^ 0.0001 15 .0 j T __- 0.0021 15 .2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 l 2200 2300 2400 2S00 2600 2700 2600 2900 3000 1 1 I 1 1 1 1 1 1 1 1 1 1 1 1 15. 0 • 1 T j u 15. 2 *~ 0.0001 \ 0.0019 15. 4 -

15. 6 —r i 1 1 1 1 I 1 I 2200 2309 21.00 2500 2600 2700 2(00 2900 3000

Fig. iV-30. ic 4329A, simultaneous fittinr at periotjs lOOOd and 50£d. -85-

1 1 1 0.4 - 1 1 1 1 1 1 1 1 1 1 1 1 i _ ] - 0.6 -•• — "—V. — -^"-^ I _.^< B - V 0.8 - ^-^ .1 "^— U.0021 1 1 I I I 1 1 1 1 1 1 1 1 1 1 1 i i 2200 2300 2400 2500 2600 2700 2800 2900 _ i i i i i i i i i i i i i i i _ -0.6 s-—^ - y \ -0.4 \ / \ - c u - B-0.2 \ 0.0023 _ y/ 0.0 > >>. i a y* _ - ^_ ^—^ 0.2 i i i i t i i i i i i 1 1 i i i 2200 2300 2400 2500 2600 2700 2800 2900 i i i i i i i i i i i i 15.0 I V 15.2 0.0023 \. lb.4 i i i i i i i i i i i iii" 2200 2300 2400 2500 2600 2700 2800 2900 i i i i i i i i i i i i i i i I 15.6 15.8 B 16.0 - 0.0023 \ S. ir lY 16.2 ^ J x -—Y*'^ '- i i i i I i . i i 1 1 1 1 2200 2300 2400 2900

2200 2300 2400 2500 2600 2700 2800 2900

Fig IV-34. MK 50, fitting at long period of 400d. -86-

-0.2 - U-B 1.0012 1.0134 >.0O94

2200 2300 2*00 2S0O 2600 2700 2Í00 2900 3000 3100 _ 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 _ 14. 2 - T 14. 4 - A /N 14. 6 u A /\A 14. 8 '.0011 1.0134 15. 0 (.0095 - \lA A f\ /KAv / v 15. 2 1 :

15. 4 \fY - WV i i i i V 1 1 1 1 1 1 1 1 i i i i i i 2200 2300 2*00 2500 2600 2700 2600 2900 3000 3100

Fig. IV-45. NGC 6814, simultaneous fitting at periods and 75d. -87-

i i 1 i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 13. 4 - - I - - X . - •—••••••• s 13. 6 _ - 1 1 . B I 1 » I « 1 0.0001 13. 8 - I

• 1 1 1. 1 1 1 1, 1 1 1 1 1 • • 2 300 2*00 2S00 2600 2700 2600 2900 3000 31 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 l~~ 1 1 r T 3 12.8 - - I B I ' — 13.0 1—• • _ - JL. u I -^ I 13.2 - I 0.0003 i 13.4 "III I 1 1 1 1 1 1 2300 2W00 2S00 2600 2700 2800 2900 3000 3100

Fig • lv-58. NGC 7469, fitting at lonn period of "lOOOd.

B 0.0001 13.8 > .'.0081

2300 2V00 2500 2600 2700 2B00 2900 3000 3100 I I I I I I I I I I I I I 1 12.8 u j.0004 0.0080 13.4 - J I till 2100 2100 2S00 2600 2700 2*00 2900 3000 3100

Fig> IV-59. NGC 7469, simultaneous fitting at period lOOOd and 125d. -88-

Tfae 1051 3 Period of the Interacting Binary White Dwarf AM CVn*

J.E. Solheim1, E.L. Robinson2, R.E. Nather and S.O. Keppler +

The close binary system AM CVn consists of two white dwarfs; the lower mass white dwarf, a helium white dwarf, is transferring mass to its higher mass companion. The light curve of AM CVn has a double humped variation with a period of 1051 s that previously was identified with the orbital period of the system. An earlier measurement of the 1051 period seemed to show that it was increasing rapidly to be easily understood. We have, therefore, remeasured the rate of change of the 1051 s period. We find that the period is changing two orders of magnitude more slowly than previously -12 -1 thought: dP/dt • (-3.2 ± 0.6)10 ss . Since the mass losing star in AM CVn is a white dwarf, the orbital period of the system must be increasing. We have found that the 1051 s period is decreasing, and, therefore, it cannot be caused by orbital motion. We reinterpret the 1051 s period as the rotation period of the accreting white dwarf, which must then be magnetized. We have also found a 1011.4 s period in the light curve that may be related to the orbital period, but cannot itself be the orbital period. Finally, we show that the double humped light curve may really be a single humped light curve with a period of 525.5 s.

*Astron. Astrophys. JI35 (1984) 1. +0n leave from IF-UFRGS. 1 Institute of Mathematical and Physical Sciences, University of Tromst), P.O.Box 953, N-9001 Transo*, Norway. 2 McDonald observatory and Department of Astronomy, University of Texas at Austin, Austin, TX 78712, USA.

The ZZ Ceti Star GD 385 Revisited* S.O. Kepler1*

We have observed the ZZ Ceti star 6D 385 with a high-speed two-channel photometer for 62.5 hr during the last 4 years. We demonstrate that, at least in 1982, its light curve was composed of three separate pulsations with periods of 256.127 s, 256.332 s, and 128.115 s, and constant semiamplitudes of 1.14Z, 1.09Z, and O.37Z respectively. The maximum semiamplitude of the 256 s pair was about 3.5Z from 1978 to 1981, but only 2.2Z in 1982. The amplitude of the 256 s pulsation changes therefore on a time scale of years, -89-

perhaps because of beating of extremely close pulsations, perhaps because of nonlinear effects.

*The Astrophysical Journal ^78 (1984) 754. +0n leave from IF-UFRGS. 1 Department of Astronomy and McDonald Observatory. The University of Texas at Austin.

The Distribution of Interstellar Extinction Near the Sun

C. Jaschek* and J.R. Ducati+

Photometric data in the uvbyP system is used for 3713 stars to map the distribution of color excesses up to 500 parsecs from the Sun, producing a series of diagrams for layers aligned with the galactic plane. Individual clouds are detected, with a mean diameter of 5.8 parsecs, while cloud complexes have a mean dimension of 100 pc. From the maps it seems that interstellar medium near the Sun presents regions of non-negligible extinction, while the Sun itself is embedded in a diffuse cloud, or slightly off its border. A large scatter in the distribution of E(b-y) is conspicuous, with a mean extinction of A » 0.38 up to 500 pc.

*Centre de Données Stellaires, Observatoire de Strasbourg, France. +0n leave from IF-UFRGS, Brazil. {Partially supported by CNPq, Brazil.

BV Surface Photometry of the Southern Galaxies NGC2855 and NGC4507 T. Storchi Bergmann, M.G. Pastoriza and M.F.S. SchrOder

This work presents some results from B and V photographic photometry obtained for the galaxies NGC2855, classified in the Second Reference Catalogue of Bright Galaxies (RC2, 1976) as (R)SA(rs)0/a and NGC4507, classified as SBab(rs)I (Sandage and Brucato, 1979). The photographic plates were obtained with the Cassegrain Camera attached to the 1.6 m telescope of Observatório Astrofísico Brasileiro, at Pico dos Dias, MG, Brazil. Part of the reductions was made using the PDS microdensitometer of Observatório Nacional, CNPq, Brazil and the software developed by da Costa et al (1982) -90-

and another part using the Zeiss-Jena microdensitometer of Instituto de Fisica-UFRGS. Isophote maps (figures 1 and 2) and luminosity profiles were obtained, both in B and V for the two galaxies, as well as B-V color index profiles. The total apparent magnitudes (B_ and V_) and color indices were determined. Distances (A) were calculated from radial velocities obtained from RC2 for NGC2855 and Martin (1976) for NGC4507, adopting H • 85 km/s/Mpc, and absolute magnitudes 00 obtained after correction for internal and galactic absorption and redshift (RC2, 1976). These data are listed in Table I, together with the values for the major (a) and minor (b) diameters corresponding to the isophotal level listed in the last column of the table. From several radial profiles, equally spaced in angle, an "elliptically averaged" (Boroson, 1981) profile was obtained for each galaxy. From the average profiles, average B-V profiles were also determined. A tentative least squares fitting to the average B profile was made using the method developed by Kormendy (1977), which fits a de Vancouleurs (1984) curve for the bulge and an exponential curve for the disk (Freeman, 1970). The parameters p , r , u and r of the adjusted fitting functions are listed in table II. Figure 3 shows the B average profile for NGC2855 and figure 4 for NGC4507. Crosses represent the observed profile, light solid lines the functions fitted to the nuclear and disk regions and strong solid lines the sum of the nuclear and disk functions. For NGC2855, the elliptically averaged B profile appears to be composed of an extensive nuclear bulge with a luminosity distribution obeying the r 1/4 law which dominates the profile until 40 arcseconds, where the contribution of an exponential disk begins to become important. In the intermediate region appears a brighter component due to a fragmented ring and possibly to a lens component (de Vancouleurs, 1980). The B-V profiles show that the average color of the nuclear region is about 1.2, reaching about 0.75 in the ring region. For NGC4507, the elliptically averaged B profile appears to be composed of: a) a nuclear bulge obeying the r 1/4 law dominating the profile until 11 arcseconds; b) an exponential disk extending from the center to the outer regions; c) a superposed contribution from 5 to 10 arcseconds due to the bar; d) a strong superposed contribution from 15 to 34 arcseconds due to the two spiral arms. -91-

Boroson, T., 1981. Ap. J. Suppl. 46_, 177. De Vancouleurs, G. 1948. Ann. d'Ap., U.t 247. De Vancouleurs, 6. and Buta, R., 1980. A. J. 85_, 637. De Vancouleurs, G. et al, 1976. Reference Catalogue of Bright Galaxies. Freeman, K.C., 1970. Ap. J. 85, 794. Kornendy, J., 1977. Ap. J. 2]7, 406. Martin, W.L., 1976. M.N.R.A.S., jj[5, 633. Sandage, A. and Brucato, R., 1979. Astron. J. 84_, 472.

Table I - Photometric Parameters

NGC Type BT VT A(Mpc) Mg a(Kpc) b(Kpc) V^ 2855 (R)SA(rs)O/a 12.42 11.44 19.53 -19.42 11.2 8.55 24.50 4507 SBab(rs)I 13.05 12.22 38.92 -20.43 10.06 7.60 24.85

Table II - Parameters of Least Squares Fitting for B Average Profiles arcsecond. , arc second.. NGC re( Kpc ) V Kpc ' 21.95 17.14 23.08 35.71 2855 1.60 3.34 5.84 21.22 18.17 4507 1.10 22.09 3.43

(b) NGC 4507- V PLATE

Fig. 1 18

20 30 40 30 60

NGC 2855-B average profile I -93- I

10 20 30 40 50 60 r(orc sec) Fig. 4 NGC 4507-B average profile

B, V, and DDO Photometric Observations of Red Variable Stars* T. Storchi Bergmann, Silvia H.B. Livi and Roberto D.D. Costa

Light curves of the red variables L~ Puppis, R Carinae, and S Carinae in the region of the spectrum covered by the B, V, and DDO photometry are presented. The behavior of the DDO color indices and their meaning for this type of star are discussed. S Carinae shows a different behavior from the other two stars that seems to be due to a population effect.

*Astrophysics and >pace Science J00 (1984) 341.

Light and Line Profile Variations due to r-mode Pulsations with an Application to the ZZ Ceti Star G117-B15A

S. 0. Kepler

We present a general formulation for the effects of r-mode nonradial pulsations on the light curves and line profiles of a slowly rotating star, given a pulsation model, and model atmospheres. We show that the temperature perturbation, the gravity perturbation and the light variations are proportional to the spheroidal component of the displacement, while the -94-

velocity perturbation is proportional to the toroidal component. Therefore, when calculating the observable effects of r-mode pulsations, it is necessary to include both the toroidal and the spheroidal components of the displacement in the calculations. We apply our formalism to the pulsating DA white dwarfs, known as the ZZ Ceti stars. Specifically, the ZZ Ceti star G117-B15A has a peculiar period structure which led Kepler et al (1982) to propose its pulsations were r-mode pulsations. We observed the wings of the HY line of G117-B15A photometrically and compared our theoretical results with the observations. Our results indicate the observed variations of G117-815A are not caused by r-mode pulsations, but are consistent with g-mode pulsations.

BV Surface Photometry of the Galaxies NGC6769, 6770, 6771 T. Storchi Bergmann, M.G. Pastoriza and M.F.S. SchrHder

B and V photographic plates from this group of galaxies are being obtained at the 1.6 m telescope of Observatório Astrofisico Brasileiro, Pico dos Dias, MG, Brazil, in order to study the structure of the galaxies in B and V: luminosity distributions, to separate different populations, study the behavior of the B-V color index across the galaxies. Photometric reductions of two of the plates were carried out using the Zeiss-Jena microdensitometer of Instituto de Física-UFRGS. Isophote B and V maps, as well as the following photometric parameters, listed in the table below were obtained for each galaxy: integrated B (IIL) and V apparent magnitudes, total color index (m_-m ), absolute magnitude (M_), major (D) and p V D minor (d) diameters dimensions at the listed outer B isophote level (pn), in a arcseconds and kiloparsecs. The galaxies NGC6769 and NGC6770 are clearly in interaction, showing common iscphotes. There is need of longer exposition plates to show if there ace common isophotes also including NGC6771 at lower isophotal levels and alto need of shorter exposition ones to better define the nuclear regions. i i Table Photometric Parameters

NGC mj mB-mv Mg D(Kpc) d(Kpc) wB 6>69 12.70 0.65 -21.27 130.0 93.0 24.86 28.1 20.1 6770 12.91 0.71 -20.97 174.0 128.0 24.86 36.7 27.0 6771 13.76 0.90 ^20.25 143.0 34.5 25.17 33.4 8.1 -95-

Age Determination of HII Regions of the LMC and SMC*

M.V. Copetti, H.Â. Dottori, E.L. Bica, M.G. Pastoriza

HII region models were constructed which take into account: 19) A burst for the formation of the ionizing association; 29) Different Salpeter's initial mass function (lãx S3) and upper stellar mass limit (30 S M /M £120); 39) Models of stars evolution with and without mass loss (Maeder, 1980, Hell ings et al 1981). From these models the temporal evolution of the Hg emission line equivalent width (Wu ), the ratio of the forbidden lines A4959, X5007 [OIII] to Ho, and of the He , H+ zones volume ratio (R) was obtained. It was found that Wu , [OIIIJ/H and R decrease as a function of the time and consequently they are P good age indicators. Some of the models appropriate for the LMC are shown in figures 1.

/.*•: ire'

Figures 1: Evolution of WH , [0III]/H. and R as a function of the time. ng &

Measurements of WH for 29 regions of the LMC (Dottori and Bica, 1981) were analized using the models. Models with x-3 can be disregarded because they are incompatible with Wg higher than 90 X, which are common in the LMC.

For x-2.5 the maximum WH is around 200 % and is not consistent with the Hg values found in 30 Dor. and NGC 2032. Values of 1i\iZ appear to be compatible with data from all regions and the choice of x within the interval does not significantly affect the scale of ages. For WH < 200 % (26 of the regions) the M also do not influence the age determination. In figure 2 we plot the -96-

histogram of ages for X 1.5 and of M - 60 M , which indicate u • a burst of stars formation with highest activity about 6.0 to 6.5 x 10 years ago, and with a duration of 1.5 to 2.0 x 10 years, measured at half maximum. Ratios [OIII/H and R were obtained for 11 HII regions of the LMC from data of Dufour (1975). The mean age obtained through these two parameters are very 2 - similar (The limits are 2.2 and 4.0 x 10 years assuming M «30 M and 60 M respectively). These ages are smaller than those ob- 6 AGE [1O YR] tained from Wu , which may be 6 related to the fact that the two Figure 2: Histogram of formation of samples have a few objects in HII regions in the LMC. common. For the SMC, data on [OIIIJ/H. for 12 regions (Dufour and Harlow, 1977), lead to a mean limit of ages of 1.4 and 3.0 x 106 years for M - 40 M and 100 M respectively. We emphasize that the dispersion around these ages is very small, suggesting that all the regions were formed simultaneously.

Dottori, H.A.; Bica, E.L.D., 1981, Astron. Astrophys. 102, 245. Dufour, R.J., 1975, Astrophys. J. 195, 315. Dufour, R.J.; Harlow, W.V., 1977, Astrophys. J. 216, 706. Hellings, P.; Vanbeveren, D., 1981, Astron. Astrophys. 95, 14. Maeder, A., I960, Astron. Astrophys. 92, 101. *I.A.U. Symposium, N9 108. "Structure and Evolution of the Magallanic Clouds", edited by S.V. den Bergh and K. de Boer, 1984, 383.

Age Determination of Galactic and Extragalactic HII Regions M.V.F. Copetti, M.G. Pastoriza and H.A. Dottori

The HII regions evolutive models of Copetti et al were compared with observational data of HII regions in Magellanic Cloud*, M33, M101, Milky Way -97-

and of "isolated extragalactic HII regions". The principal results are: 1. IMF with x - 3 or 2.5 are inconsistent with a large number of HII regions; 2. The more uniform age distribution of isolated extragalactic HII regions obtained through IMF with x - 2 suggest that this value is «ore realistic that X • 1 or 1.5; 3. The HII regions age estimatives indicate a burst of star formation about 5.5 ± 1.0 x 10 years ago in LMC and about 2.3 ± 0.9 x 10 years ago in SMC; 4. The observed [0III]/H. gradient in M33 and M101 must be P caused by color temperature variations of the HII regions ionizing field radiation; 5. Although the variations of Wu and [OIIIJ/H. may be explained qualitatively by metallicity gradients in M33 and M101, the values are only compatible with evolved HII regions with ages between 2 and 5 x 10 years; 6. The ages obtained for galactic HII regions suggest a large scale star formation more recent in the Orion spiral arm that in the Sagittarius one.

HII Regions Age Indicators M.V.F. Copetti, M.G. Pastoriza and H.A. Dottori

The evolution of some HII regions properties, as the relative volume R of the He* and H+ zones, the equivalent width WJJ of the Hg emission line and

the ratio [0III]/H. of the lines [0III]AX4959, 5007 to Ho, was studied through p P models that take into account: a single burst for the formation of the ionizing association with different initial mass function IMF (1 Í X í 3) and upper stellar mass limits (30 ÍM/M Í 120); distinct chemical composition models of stars evolution with and without mass loss. It was found that WJJ , R and [0III]/H. decrease monotonically as a function of the time and conse- p quently they are good HII regions age indicators.

DDO Integrated Photometry of Globular Clusters and Initial Chemical Evolution of the Galaxy* Eduardo L.D. Bica and Miriani G. Pastoriza

Integrated photometry of 91 galactic globular clusters was carried out with the UBV and DDO systems. A method to determine reddening is presented. Metal abundances were obtained by means of a calibration of C(42-45) vs[Fe/H]. Thirteen other clusters whose metallicity values were made compatible with -98-

those observed here, were added to the sample totalizing a homogeneous set of [Pe/H] estimates for 104 globular clusters. This sample is used to analyze the •patial distribution of metallicities. An estimate of the intrinsic metal abundance frequency distribution of the globular cluster system is provided. The chemical properties of the globular cluster system are compared with one- zone-chemical-enrichment model8 which take into account gas loss from star formation regions. It is concluded that these models cannot describe the complete chemical enrichment of the globular cluster system.

•Astrophysics and Space Science 91 (1983) 99.

DDO Photometry and Metallic Abundances of E and SO Galaxies and Globular Clusters of the LMC and SMC* Horacio A. Dottori, Miriani G. Pastoriza and Eduardo L.D. Bica

Metallicity of 8E and SO galaxies as well as that of red globulars of the LMC and SMC were obtained by means of DDO integrated photometry calibrated with galactic globular clusters (Bica and Pastoriza, 1893; hereafter referred to as Paper I). A correction was obtained in order to reduce the colors of the galaxies to zero redshift. The relation metallicity vs M for the galaxies is analyzed (adding to our sample the observations of McClure and Van den Bergh, 1968; and Faber, 1973a). For the Magellanic Clouds we found metallicity ranging from intermediate to poor.

•Astrophysics and Space Science 91 (1983) 79.

DDO Photometry on Red Giants in the Open Clusters NGC 2232, NGC 2287, and NGC 2451» Miriani G. Pastoriza and Ursula 0. RBpke

From DDO photometry combined with U, B, V photometry of red stars in the open clusters NGC 2232, NGC 2287, and NGC 2451, tha mean color axcess E(B-V), tha distance modulus, and tha mean natal abundance [Fa/H] ware derived for tha clusters. Tha physical parameters, surface gravity, affactiva temperature, and spectral type wars also obtained for tha rad stars. Estimation of aga yielded -99-

1.1 x 10 yr for NGC 2287, and for HGC 2451, 4.8 x 10 . The cluster NGC 2232 k- 9 p should be older than 10 yr.

*The Astronomical Journal Vol. 88, N9 12 (1983).

PG 1116+158 D.E. Winget, R.E. Nather and S.O. Kepler* Department of Astronomy and McDonald Observatory, University of Texas, USA

The strong-line (He I) dB white-dwarf star PG 1116+158 is a pulsating variable star. This brings to three the number of known pulsating dB white dwarfs. The star was observed by using a high-speed, two-star photometer with an RCA-8850 tube in unfiltered light on the 2.1-m telescope. The lightcurve has a quasi-period of .1000 s with a peak-to-peak amplitude of 0.06 mag. Pre- liminary power spectra of two runs (for 2.8 hr on Feb. 6 and for 1.9 hr on Feb. 28) indicate significant power near 1100 s and 800 s with fractional amplitudes near 1.0 and 0.4 percent, respectively. The star is a Palomar-Green survey object with B- 16.1, and co-ordinates and finder charts are available on request to us at TWX 910-874-1351 TEXASTR0 AUS.

*0n leave from Instituto de Física-UFRGS, Brazil.

Relationship» of a Growing Magnetic Flux Region to Flares* S.F.Martin, R.D.Bentley, A.Schadee, A.Antalova, A.Kucera, L.Dezso, L.Gesztelyi, K.L.Harvey, H.Jones, S.H.B.Livi+ and J. Wang Solar Astronomy 264-33, California Institute of Technology, Pasadena, CA 91125, USA

Some sites for solar flares are knwon to develop where new magnetic flux emerges and becomes abutted against opposite polarity pre-existing magnetic flux (review by Galzauskas). We have identified and analyzed the evolution of such flare sites at the boundaries of a major new and growing magnetic flux region within a complex of active regions, Hale No. 16918, This analysis was done as a part of a continuing study of the circumstances associated with -100-

Flares in Hale Region 16918, which was designated as an FBS target during the interval 18 - 23 June 1980. We studied the initiation and development of both •ajar and minor flares in Ha images in relation to the identified potential flare sites at the boundaries of the growing flux region and to the general development of the new flux. This study lead to our recognition of a spectrum of possible relationships of growing flux regions to flares as follows: (1) intimate interaction with adjacent old flux - flare sites centered at new/ old flux boundary, (2) forced or "intimidated" interaction in which new flux pushes old field having lower flux density towards a neighboring old polarity inversion line where a flare then takes place, (3) "influential" interaction - magnetic lines of force over an old polarity inversion line, typically containing a filament, reconnect to the new emerging flux; a flare occurs with erupting filament when the magnetic field overlying the filament becomes too weak to prevent its eruption, (4) inconsequential interaction - new flux region is too small or has wrong orientation for creating flsre conditions, (5) incidental - flare occurs without any significant relationship to new flux regions.

*Adv. Space Res. 4_ (1984) 61. +0n leave from IF-UFRGS, Brasil.

Ephemeral Regions vs. Pseudo Ephemeral Regions

S.F. Martin, S.H.B. Livi*, J. Wang** and Z. Shi** Solar Astronomy, California Institute of Technology, USA

Our new studies of the quiet sun reveal that ephemeral active regions constitute a minority rather than a majority of all the short-lived, small- i scale bipolar features on the sun. We retain the definition of an ephemeral region as a feature which appears to originate as a compact bipole and grows as a unit in total flux for at least a short time after its birth. In contrast to the recognized patterns of growth and decay of ephemeral regions, we illustrate various examples of the creation of other temporary bipoles nick- named "pseudo ephemeral regions". We show that the pseudo ephemeral regions are the consequence of combinations of small scale dynamic processes of the i quiet sun including: (1) fragmentation of network magnetic fields, (2) the separation of opposite polarity halves of ephemeral regions as they grow and -101-

evolve, and (3) the coalescence of weak network or intra-network magnetic fields. In long-exposure videonagnetograns (-1 min.), having spatial resolution of 2-5 arc seconds, the pseudo ephemeral regions outnumber the real ephemeral regions by about a factor of 2. These new observations offer the possibility of resolving the discrepancies that have arisen in the association of ephemeral regions with X-ray bright points. We suggest that many X-ray bright points may be related to those pseudo ephemeral regions which have begun to exhibit magnetic flux loss. We also suggest that vector magnetograms should reveal distinct differences between real and pseudo ephemeral regions similar to the differences that are sometimes seen in Ha filtergrams. Ha images show the opposite polarities of some ephemeral regions to be connected by fibrils or arch filaments. In contrast, the pseudo ephemeral regions sometimes reveal a fibril, like a small filament, dividing the opposite polarity fields, but no well-defined fibrils connecting the opposite polarities.

*0n leave from IF-UFRGS, Brazil. **Beijing Observatory, The Academy of Sciences, Beijing, China. PHYSICS EDUCATION I -103-

Í Laboratory Teaching Materials for Secondary Schools* t • t R. Axt, V.H. Guimarães and B. Buchweitz

I The problem Even if many secondary teachers recognize that experimental work at ; secondary level is fundamental for increasing the quality of Physics teaching, in fact most schools offer very little laboratory activity. Conventional laboratory materials are generally demonstrative, time consuming for preparation and little effective in engaging the student actively. Acquisition and maintenance of such materials use to be expensive \ and sometimes very difficult to accomplish. In many schools, as a result of discontinuous laboratory activity, components are spoiled or lost. Perhaps as a consequence, school administra- tors generally show little interest in acquiring new laboratory materials. Besides this, the educational system makes the teacher to run from class to class, so that his laboratory teaching plans are left behind from one day to another. In addition, one also has to take into account a shortage of qualified teachers.

Laboratory materials: a new version

Assuming that laboratory work is an important piece of Physics teaching at secondary level and that a variety of materials available in the schools' laboratories are inadequate for practical activity and dissociated from reality, we decided to develop laboratory materials, in the form of kits, for experimental teaching of Mechanics, Electricity & Magnetism and Optics. Our purpose was to produce simple materials, which could be easily handled, without unnecessary sophistications, aiming at a student-centered teaching and at an enrichment of the learning environment. The apparatus should encourage teachers to use it: they shouldn't have reasons to fear laboratory work. The apparatus should be of good quality and nevertheless not too expensive. It should be possible to collect it safely and rapidly. The conciliation of all these characteristics involved some definite options: a) In order to involve students actively we preferred to multiply the apparatus instead of offering a great number of different experiments. b) In order to reduce costs, the measuring instruments were simplified and many components were used in more than one apparatus arrangement. -104-

c) In order to supply the lack of a good (and safe) laboratory room and to facilitate the displacement of the material, it was packed in wooden boxes, each one of which containing apparatus for five times twelve different experiments. d) In order to help teachers to overcome possible defficiencies in laboratory work experience, a teacher's guide was written for each unit. Three units (Mechanics, Electricity & Magnetism and Optics) introduce experiments about movement, forces, energy, fluids, elementary circuit elements, magnetic and electromagnetic phenomena and optical phenomena. Most experiments are quantitative and, as there are five apparatus available in each kit, enquiry methods are suggested as a common teaching practice.

Results The apparatus kits were multiplied and lent to physics teachers. In two years of existence, this project has introduced laboratory classes in more than twenty secondary schools, many of which don't have any equipment at all. Reports account for greater involvment of students in learning activity, students feeling physics closer to real life, less learning from textbooks and teachers feeling stimulated by well succeeded laboratory classes. The simplicity of the apparatus is pointed out by students and teachers as an important aspect, because it reduces the chance of losing sight of physical phenomena and facilitates concept comprehension.

*Work partially supported by FINEP.

Experimental Physics Teaching in Secondary Schools; an Attempt to Make it Feasible**

R. Axt and V.H. Guimarães

It is discussed the role of laboratory teaching in schools examining contributions of learning theories, and the nature of scientific knowledge itself. In addition it is described a specific project aimed to give support to experimental teaching of physics in secondary schools of Rio Grande do Sul.

*Cicncia e Cultura 3£(1) Jan. 1985 [in Portuguese]. •Work partially supported by FINEP. -105-

Equipment for Secondary Schools - Teacher's Guide - Vol. II - Electricity R. Axt and V.H. Guimarães

This laboratory text was written for secondary teachers as a guide for the equipment unit about Electricity and Magnetism developed in the project described under the title of Laboratory Teaching Materials for Secondary Schools.

•Internal edition, 1983. 23 p. [in Portuguese]. •Work partially supported by FTKEP.

Equipment for Secondary Schools - Teacher's Guide - Vol. Ill - Optics** B. Buchweitz and R. Axt

This laboratory text was written for high school teachers as a guide for the equipment unit on Optics developed in the project described under the title of Laboratory Teaching Materials for Secondary Schools.

^Internal edition, 1984. 30 p. [in Portuguese). +Work partially supported by FINEP.

Concept Maps as Instruments for Learning Evaluation** M.A. Moreira

Concept maps are diagrams stressing the conceptual structure of a piece of knowledge. By asking the student to draw a concept map for a given topic the teacher gets qualitative information about the kinds of relations and meanings the learner assigns to the concepts involved in such a topic. In addition to describing what is meant by concept mapping, the paper proposes it as a nontraditional technique of evaluation and presents several examples of concept maps drawn by college students as evaluation tasks.

*Educação e Seleção, _U) (Jul/Dec): 17-34, 1984 [in Portuguese]. •••Work partially supported by FINEP. -106-

Concept Map» as Tools to Investigate Cognitive Structure in Physics** W.E. Ahumada G.

A study in which concept maps and interviews were used as nontraditional learning evaluation instruments, in order to investigate the evolution of the learner's cognitive structure in the area of Electricity and Magnetism at introductory college level, is described. Research findings suggest that these instruments are really useful for such a purpose, that the student's cognitive structure tends at the end of instruction toward a hierarchical configuration and that the kind of approach to content organization used in the instructional material has a strong influence on concept learning.

*M.Sc. dissertation. Porto Alegre, Instituto de Física-UFRGS, 1983. 105 p. [in Portuguese] •«•Work partially supported by FINEP.

Experimental Activities to the Teaching of Fluid Mechanics at Introductory College Level*'*' A.V.L. Porto

A set of ten experimental activities in the area of fluid mechanics is proposed with the purpose of collaborating in an attempt of stopping a gap existent in many introductory physics courses at college level. For each one of these experimental activities a laboratory guide for student's use was prepared.

*M.Sc. dissertation. Porto Alegre, Instituto de Física-UFRGS, 1983. 102 p. [in Portuguese] •«•Work partially supported by CAPES and FINEP.

Entrance Examination: Comparison of Students Achievement in Four Areas of Physics*

Bernardo Buchweitz and Fernando Lang da Silveira

The physics multiple choice items of the entrance examination of the -107-

Federal University of Rio Grande do Sul (1974-1982) are classified in four areas - nechanics, thermodynamics, electromagnet ism and waves - in order to compare the scores of the students. A statistical analysis of the data shows that there is no significant difference among the means in these areas.

•Educação e Seleção, 7 (Jan/Jun): 43-48, 1983 [in Portuguese]

Discrimination Index of Psychometric Tests Items Correction*

F.L. Silveira

An equation that makes the discrimination index of psychometric tests items a consistency measure of item scores with total scores in remaining items is deduced.

*Ciincia e Cultura, 35(1): 78-79, 1983 (in Portuguese]

University Teaching: Texts Concerning Basic Components of Instruction*'*' M.A. Moreira (Ed)

This book is a compilation of texts on the methodology of higher education. Each one deals with a single topic of such methodology and uses a language designed to be easily understood by teachers who are not used to the educational jargon. It includes topics on teaching strategies, instructional aids and evaluation procedures. It also presents an article concerning the evaluation of teaching by the student.

*Porto Alegre, Editora da Universidade, 1983. 214 p [in Portuguese] •«•Work partially supported by PADES/UFRGS. -108-

Assessment of Content and Cognitive Structures in Physics at College Level»* M.A. Moreira and R.C. Costa

First, the theory of directed graphs (digraphs) was used to map the conceptual structure of the content, implicit in the instructional materials, in the area of electricity at college level. After this, the graphical representation of content structure, thus obtained, was compared with those obtained for the teacher's cognitive structure and the student's cognitive structure through a word association test and the multi-dimensional scaling technique. Research findings suggest mainly that the techniques used to assess content and cognitive structures might be useful tools for such a purpose.

«Assessment and Evaluation in Higher Education, £(3): 234-245, 1983. •Work partially supported by F1NEP.

A Cognitive Approach to Physics Teaching** M.A. Moreira

This book proposes the learning theory of David Ausubel as a framework for organizing the teaching of science, mainly physics. Following a fairly detailed description of Ausubel's theory, an example is given of how it can be used as a frame of reference to organize the teaching of electricity and magnetism at introductory college level. After this, advance organizers and concept maps are fully analysed as instructional aids. Finally, several techniques of assessing cognitive structure are discussed and exemplified. In spite of using physics as a vehicle to illustrate the use of Ausubel's theory as a theoretical framework to organize instruction, the book is designed to be useful to teachers of other subjects as well, including those who are only interested in a description of the theory.

*Porto Alegre, Editora da Universidade, 1983. 189 p. [in Portuguese] •Work partially supported by PADES/UFRCS and FINEP. -109-

Different Approaches to Laboratory Teaching**

M.A. Moreira and C.E. Levandovski

This book proposes three different approaches to laboratory teaching. The first one is closely related to the so called structured laboratory since programmed laboratory guides are used in it. These guides are programmed in accordance with James Gallagher's topic classification system. The second approach emphasizes the structure of the experiments by stressing the phenomenon of interest, the basic question, the key concepts, the knowledge claims and the value claims of the experiment being performed by the student. The third approach is an extension of the second because in addition to emphasizing these aspects it also tries to relate them under an epistemologic point of view. That is, it attempts to go deeper into the question of the structure of knowledge and how it is produced. The second and third approaches are based on the ideas of D.B. Gowin about the structure of knowledge. The same four experiments - simulated electric field, Ohm's law, RC circuit and electromagnetic induction - are used as examples in the three approaches.

*Porto Alegre, Editora da Universidade, 1983. 117 p [in Portuguese] •Work partially supported by PADES/UFRGS and FINEP.

Student Evaluation of Teacher's Performance; Evidences of Validity of an Instrument* F.L. Silveira and M.A. Moreira

An instrument (questionnaire) for student's evaluation of teacher's performance is proposed and validity evidences of this instrument are presented. In the validation procedure, answers from sixteen groups of students evaluating didactical behaviors of their teachers were used.

*Ciincia t Culturt, 36(3): 466-72, 1984. -1 1 0-

Imprpving University Teaching; Supporting Small Projects as a Strategy for Instructional Development* M.A. Moreira and R.V.A. Baquero

First, general considerations are made concerning different aspects of a process to improve the quality of teaching in an institution of higher education. After, PADES/UFRGS and its action in this University are briefly described before focusing on one of the strategies used by this organism as a way of actively engaging the teacher in such a process. The strategy in question is the pedagogical and financial support to the development of small projects designed to improve teaching. Finally, some data are presented concerning the use of this strategy at UFRGS during five years and some comments are made.

*Ciincia e Cultura, 36(5): 737-742, 1984 [in Portuguese].

Measuring Attitude Towards the Laboratory in Introductory College Physics*

F.L. Silveira and J.C. Gasparin

Based in the Likert method an attitude scale towards laboratory instruction in introductory college physics was constructed. Initially, the scale had 31 items. From the answers of 383 students of the laboratory courses offered by IFPUCRS , an analysis of internal consistency was carried out through factor analysis. Only one of the original scale items had to be discarded. The results as well as the reliability coefficient and other features of the total score in the scale are presented in the paper.

*Educação e Seleção, £ (Jan/Jun): 65-70, 1984 [in Portuguese]. •Institute of Physics~of the Catholic University of Rio Grande do Sul.

Teaching and Learning; Theoretical Approaches** M.A. Moreira

This book includes a set of six monographs on theoretical approaches to -111-

1earning and instruction. Each one deals with a specific author (B.F.Skinner, R.Gagné, J.Bruner, J.Piaget, D.Ausubel and C.Rogers) and is written with the purpose of being accessible to college teachers who are not familiar with the educational jargon.

*São Paulo, Editora Moraes, in press [in Portuguese]. •Work partially supported by PADES/UFRGS.

The Use of Concept Maps in the Analysis of Curriculum* Bernardo Buchweitz

This paper presents a method of curriculum analysis, which basically consists of an epistemological analysis of the methodological and conceptual structures of sources of knowledge. Special attention is given to the concept mapping technique, which can be used to analyze in detail the conceptual structures of such sources. Examples of concept maps used in different areas of knowledge are presented.

*Educação e Seleção, _10. (Jul/Dec): 3-16, 1984 [in Portuguese].

Double Evaluation of Essays; Comparing Scores**

Bernardo Buchweitz and Maria do Horto Soares Motta

The study presents a comparison between the scores of 800 students obtained in two successive and independent evaluations of a written essay. The analysis shows that different judges tend to assign different scores to the same essay.

*Educação e Seleção, H) (Jul/Dec); 83-90, 1984 [in Portuguese]. •«•Work partially supported by C0PERS0. -1 12-

Concept Maps as Instructional Tools in Physics Teaching**

S.T. Gobara

A study was carried out in order to investigate the effects of concept maps, as instructional aids, on student's learning. The study was conducted in an introductory college physics course on electricity and magnetism - Physics II, involving two groups of students. For research purposes the experiment was divided into four parts characterized by interviews with the students. In the first and third of these interviews the students were instructed with concept maps whereas in the second and fourth interviews they were requested to draw their own maps from a list of concepts randomly organized by the researchers. The maps drawn by the students together with data from the interviews were initially analysed in a qualitative way and after- wards they were also analysed quantitatively. Research findings suggest that: the influence of content organization in the textbook seems to be stronger than the influence of the model of concept map used in the instructional maps; end-of-course concept maps were different from middle-of-course maps and the difference might be regarded as an effect of instruction, particularly of the concept maps used as instructional aids; finally, a great majority of the students were highly in favor of concept maps as an instructional aid, judging them helpful in learning physical concepts.

*M.Sc. dissertation. Porto Alegre, Instituto de Física-UFRGS, 1984. 186 p. [in Portuguese]. +Work partially supported by CAPES and FINEP.

Analyses of Items of the Entrance Examination of the UFRGS-1984*

Bernardo Buchweitz, Maria do Horto Soares Mott;a and Zaida Grinberg Lewin

This book presents a general analysis of each written text and the statistical data of 520 multiple choice items used in the entrance examination of the Federal University of Rio Grande do Sul in 1984. It shows: histograms, means, and standard deviations of each test as well as the statement, the percentage of correct answers, and the discrimination index of each item. The data can be used to improve the elaboration of multiple choice items -113-

as well as to identify educational problems particularly those related to learning.

*Porto Alegre, Editora da Universidade/COPERSO, 1984. 279 p [in Portuguese]

Cognitive Mapping in Thermodynamics Through Multidimensional Scaling**

C.A. Santos and M.A. Moreira

The content of Thermodynamics at introductory college level was taught to engineering students under two different approaches. One was based on the learning theory of David Ausubel stressing progressive differentiation and integrative reconciliation while the other one was the traditional approach found on most textbooks on the subject. Word association tests were applied to the experimental and control groups before and after instruction. Data gathered with these tests originated a similarity matrix whose structure was investigated through multidimensional scaling (MDS). The MDS configurations thus obtained were supposed to provide a cognitive mapping which, in turn, was used to investigate the effect of the Ausubelian approach as compared to the traditional one.

*CONTACTOS, Mexico, 1984 [in Spanish]. •••Work partially supported by F1NEP.

Inference about the Mean Using a Set of Data: an Aspect Related to the Sensitivity of Measurement** F.L. Silveira, P.H. Dionisio and B. Buchweitz

In this work it is shown that in a measuring process the sensitivity of measurement (one half of the difference between the two nearest values that can be discriminated in a measuring process) can change significantly the mean and the standard deviation of a variable assumed to have a normal distribution. Therefore, one must be careful when one wish to construct a confidence -114-

interval for the mean only if the standard deviation of the data is larger than the sensitivity.

«Ciência e Cultura, 35(10): 1492-6, 1983 [in Portuguese]. •Work partially supported by FINEP.

Considerations on the Discrimination Index of Items in Educational Tests* F.L. Silveira

Some restrictions are raised against the discrimination index of items in educational tests. In spite of this, it is argued that it might be used in the analysis of internal consistency of tests, given that the necessary precautions are taken, because it has the advantage of being easily remembered and its meaning being easily understood by people not familiar with statistics.

*Educação e Seleção, 7 (Jan/Jun): 54-58, 1983 [in Portuguese].

The Content Analysis as a Tool of Evaluating Learning in Physics* Beatriz M. M. Zawislak

Only recently the content analysis is being used in educational area, as a tool for evaluating the written (or oral) responses of students to questions in a given field of knowledge. With this procedure, the analyst may identify the way the students think and how they know and interpret specific concepts and laws and how they apply these laws. If the questions belong to instructional classroom tests, the analyst - being the teacher - may after the results of the analysis, look for new instructional activities that can improve the identified learning difficulties. Nevertheless, little empirical work has been reported about content analysis of written responses of students to instructional classroom tests. The present study is related to this field of analysis. The subjects of this study are a group of 22 university students (male and female) that took physics lectures with the author during one semester at the Institute of Physics of the UFRGS. These students were enrolled in -1 15-

Pharmacy or Agronomic courses. The instrument of the research were the written answers of the students to an instructional test in the areas of dynamics and hydrostatics. The test was composed of 5 questions divided in 10 items and was organized following Bloom's taxonomy in only three levels: knowledge, comprehension and application. The first question - whose analyses is fully done (the others are still being worked) had three items, with the following purposes: - item 1.1 is used to measure how a student knows the concept of buoyancy force, when he presents a definition of it; - item 1.2 is used to measure his comprehension of the same concept through the indication of the parameters which define buoyancy force; - item 1.3 is presented to measure how the student use Newton's laws and Archimedes principle, when he compares the buoyancy of different liquids over a same solid object that floats each time in one of them. The responses were compared with a previous model and then classified in categories. The discussion of results was oriented 1) by a conceptual framework of the concept force and 2) by a conceptual framework of learning, both organized by the author for this research. The results showed that: 1) 41Z of the students know perfectly what is buoyancy, presenting a good definition of it as an interiction force between liquid and object. 2) 40Z presented the correct parameters of buoyancy force. Among the students who presented the wrong parameters, there was confusion between force and pressure, gravitational force and gravitational acceleration. 3) Only 4.5% (one student) applied explicitly and correctly the first law of Newton (and Archimede's principle) to answer item 1.3, thus showing that it is more difficult to apply a law than to tell it by heart. 4) Taking one student and comparing his answers to the different items, it is possible to infer if his learning was meaningful or simply mechanical, as Ausubel's definition for meaningful and mechanical learning. 5) In a next study, it would be interesting to interview some students, to give the right interpretation of their answers, as veil as to have a larger sample of students, to give more consistency to the results.

*This report is part of a research that is still being done. It was meant to be presented at VI Simpósio Nacional de Ensino de Física, taking place in Niterói, RJ, in January 1985. INSTRUMENTATION AND DEVELOPMENT -1 17-

Reliable Room Temperature Compensation for Thermocouples**

M. Fin and M.N. Baibich

We have built a reference generator for thermocouples to substitute the traditional ice-and-water baths with precision equal or better than both the baths and equivalent commercial products. Aside from precision, this project had the preocupation of using only inexpensive, readily available components. Electronically the generator may be described as a Wheatstone bridge where one of the arms is substituted by a temperature sensor (a temperature calibrated LED) and an operational amplifier operating as a voltage divider. This amplifier has high input impedance and low output impedance, and gain much smaller than one, due to the higher sensitivity of the diode as compared LO the thermocouple. As a consequence, the thermal drift characteristics o£ the amplifier are not so relevant and an inexpensive unit can be used. The sensing diode is placed in good thermal contact with the "cold" end of the thermocouple, anchored between aluminum blocks and enclosed in styro- foam insulation to avoid rapid variations of the reference temperature. This unit has been operating within the specified accuracy for over a year and no servicing was required.

*Work supported in part by CNPq, FINEP, PROPF.SP. •Published in summary form only at the 36th Annual Meeting of the Sociedade Brasileira para o Progresso da Ciência, São Paulo, SP, July 1984.

Simple D.C. Differential Resistometry for Lcug Term Experiments*

M. Fin and M.N. Baibich

In several opportunities we have been limited by precision when dealing with small changes on top of large constant signals (for example, the resistivity of amorphous metals). Even the use of a nanovoltmeter in a four terminal configuration is not sufficient to achieve the required sensitivity for the experiments. It is clear that a differential measurement was needed. We have therefore built the circuit schematically shown in the figure. -118-

45 *(* vs NV t0 nanoToltmeter

RS —« cs I polarity control

This simple bridge consists of a precision millivolt generator (VS) connected to the measuring circuit as seen above. The voltage developed at the sample(RS) from the flow of a current I from a stabilized current source (CS) is conveniently added to that adjusted at VS and measured as a difference at NV by a digital nanovoltmeter. To avoid reading of spurious thermal e.m.f.'s, both current and compensating voltage are switched simultaneously. Since this equipment was designed to operate continuously for long periods of time and we do not have available high quality (low drift) components we have mounted it in a temperature controlled environment (Tv45 C). This equipment has been operating for some time now and has shown remarkable stability and reliability. As a new development, the control signal for the switches is now coining from the automatic data gathering system (described elsewere in this report) providing truly equal statistics for each experimental point taken.

•Work supported in part by CNPq, FINEP, PROPESP-UFRGS.

AC Susceptometer for Measurements in the 4 to 300 K Temperature Range* W.H. Schreiner, J. Schaf and W.A. Ortiz*

An AC susccptomcter for initial and transverse susceptibility measurements was developed. The susceptometer is based on the traditional Hartshorn* bridge, but the expensive Decatransformers were substituted by a simple -1 19-

electronic balancing circuit. The temperature range for the magnetic measurements varies from 4 to 300 K. The cryostat was built based on the superisolated construction principle. Liquid nitrogen is not needed for the thermal shielding.

•Supported in part by CNPq and FINEP. •Dept. of Phyaics, Federal University of São Carlos, São Carlos, SP, Brazil.

Superisolated Dewars

J. Schaf and W.H. Schreiner

Several superisolated dewars were built for resistivity, magnetometry, magnetostriction and susceptometry experiments. These dewars dispense the use of liquid N_ for thermal shielding purposes and are thus of low magnetic noise and suited for small gap electromagnets. The boil-off rates are typically of 0.1 l/h. for liquid helium for dewars with tails for magnetic measurements.

Low Temperature Implantation Chamber* P.F.P. Fichtner, I. Bello and M.N. Baibich

A low temperature implantation chamber was built for multipurpose use. It allows a temperature control between 20 and 350 K, measurement of the electrical resistance in situ during the implantation, and use of the Rutherford Backscattering technique (RBS). The chamber can hold three samples (25x25 mm2 each) on a cold plate. This plate is temperature controlled through a resistence heater and pressure control of the He gas in a heat exchange chamber between the sample holder and a cold source. This cold source is a He closed cycle refrigerator which is at a fixed temperature of 17 K. Electrical resistivity is measured using the AC bridge described elsewhere in this report. The RBS measurements are performed using a solid state detector which is at 145° with respect to the beam direction.

*Work partially supported by CNPq, FINEP and PROPESP-UFRGS. -120-

Data Acquisition System for Susceptibility and Resistivity Measurements F. Ogiba, M. Fin and M.A.Z. Vasconcellos

Using a personal microcomputer based on the Z-80A microprocessor we have built a system capable of performing automatic measurements of susceptibility or resistivity versus temperature. The microcomputer reads a digital voltmeter and/or a digital clock (built in our electronics lab) through its BCD outputs using a parallel interface type PI0-Z80A. Also, it controls inversion keys, an X-Y recorder and data recording on a cassette tape. The program to execute the periodic readings is written part in BASIC and part in machine language (Assembler Z80).

Temperature Measurements Using Resistance Thermometers at Low Temperatures** M. Fin and M.N. Baibich

The resistance thermometers usually employed at low temperatures (Ge, carbon glass, etc.) show resistance curves which are approximately logarithmic with temperature. The conductivity, however, is almost a linear function of temperature. This has led us to build a system that measures, using a commercial voltmeter, the conductivity. The system is composed of a square wave generator, a stabilizer for the signal amplitude, a differential amplifier and an active filter. The square wave generator uses digital technology, is crystal-stabilized and centered in a frequency which is not a multiple of line frequency. The stabilizing circuit uses an operational amplifier fed back by the temperature sensor so as to maintain constant voltage over the probe resistance. This ensures that any change in the temperature translates as a change in the current f".owing in the circuit. This current is in fact proportional to the conductivity of the sensor, and is measured by the voltage drop across a known resistor (RS) in series with the thermometer. The signal from the -121-

standard (RS) is amplified differentially and the output goes to a very narrow pass-band filter, centered at the generator frequency. The output of the filter, at this point a sinusoidal wave, can be measured by a standard commercial AC voltmeter. The design adopted here allows for the use of rather inexpensive parts and is imnune to thermal drifts (in first order) and line or RF pick-up. The system has been mounted with a DC output as well as the AC output, to allow simultaneous recording of the temperature, and LED's indicate both over- range or underrange conditions. The unit has shown remarkable characteristics when tested with standard resistors (changes AR/R ^ 1O~ are visible) and seems to introduce errors smaller than those coming from calibration of the thermometers in actual operation.

*Work partially supported by CNPq, FINEP, PROPESP-UFRGS. •Published only in summary form in the Annals of 36th Annual Meeting of SBPC- Sio Paulo, SP, Brazil.

Proportional Temperature Control for Resistance Furnace**

M. Fin and M.N. Baibich

We have developed a temperature stabilizing system composed of a proportional temperature controller, a resistance furnace and a power source. The temperature controller has three basic stages: one signal amplifier for the thermocouple,a comparator stage and an output stage for interfacing with the power source. The first stage is made with an operational amplifier with high thermal stability externally compensated in frequency to reject spurious signals and has adjustable gain to conform to different thermocouples. The comparator is also an "op. amp." with adjustable gain. The reference for this stage can be selected between an internal, highly stable source or an external generator from a switch in the front panel. Adjusting simultaneously the gains of the first two stages one can obtain the required temperature responses at the furnace according to the "thermal inertia" of that particular oven. We have used a modified SORENSEN Mod. DCR 80-18 constant current source to drive the furnace. Using a ramp generator at the external mode, controlled rates of heating can be obtained. The system described above has been operating for over a year, almost -122-

continuously. Several tests have shown that the maximum excursion of the temperature, at % 800 °C, is around 0.5 °C. Heating rates for the oven in use go up to t> 20 C/min, smaller units could certainly h~ve higher rates.

•Work supported in part by CNPq, FINEP, PROPESP-UFKGS. •Published only in summary form in the proceedings of 36th Annual Meeting- SBPC, Sio Paulo, SP (1984).

Low Frequency AC Differential Resistance Detection* M. Fin and N.N. Baibich

The measurement of small deviations in resistivity with temperature usually involves a rather expensive set-up, including some imported equipment. Due to the present economic situation of the country, this equipment is practically impossible to obtain. We have therefore designed a simple bridge operating at a constant low frequency that would be able to give the accuracy required with a commercial digital voltmeter (made in Brazil) as detector. The block diagram bellow shows the essential features of the circuit.

current source -1 23-

The system is essentially formed by a crystal stabilized square wave generator that drives a linear current source. The signal is fed to the measuring circuit as shown in the figure. Resistor R gives the scale for the s current flowing; adjusting R one can obtain zero reading at the output of the active filter, which is centered at the generator frequency. Any variation in S (with temperature or magnetic field or other) will be detected, free of noise, with augmented sensitivity at V. The absolute value of S can also be obtained shorting R . z *Work supported in part by CNPq, FINEP, PROPESF-UFRGS.

A Microcomputer Data Aquisition System for Pulsed Dye Laser Spectroscopy Experiments J.A. Lisboa, J.A. Pasqual and R.E. Francke

The high peaks power, wide range of tunability and short pulse duration of typical nitrogen pumped tunable dye laser makes it very simple to generate a large amount of spectroscopic data from just about any molecule. However, the low repetition and large power fluctuations of the laser pulses requires sampling techniques. A widely used system is an analog one composed by a "box- car" integrator and a strip-chart recorder, where the data treatment is realized "by hand" from the graphics obtained. To improve the treatment and data acquisition on such experiments we have developed a special interface from the laser system to an inexpensive microcomputer (TK-85). It is formed by four simultaneous acquisition channels, each one composed by a rapid peak detector. Each peak detector can freeze the amplitude of pulses as short as 10 ns while the four channels are multiplexed to the input of an amplifier whose gain is controlled by the microcomputer. After this amplifier an 8 bit A/D converter digitizes the amplitude of each pulse which is then transferred through a Z-80 PIO to the microcomputer RAM for subsequent analysis. With such configuration the amplitude of rapid pulses can be digitalized by an A/D converter and microcomputer which operates on a much slow time scale (clock frequency «3.2 MHz) and a widely range of input signal level can be conditioned to a level where the 8 bit A/D converter works near its maximum resolution. -124-

Magnetoanisotropies in Fe-Si Foils and its Utilization in Force Transducers Solon Pereira da Cruz Filho* and Flavio Pohlmann Livi

A configuration was developed for magnetoelastic force transducers nade with oriented silicon-iron sheets, in which the relative orientations of the windings, the easy magnetization axis and the stress direction are design paraneters. An adequate choice of the relevant angles allows the transducer to work in an intrinsecally linear region of the response curve. The developed prototype has a full scale value of 1000 N but the configuration nay in principle be extended to any range.

*PPGEMM-UFRGS, Porto Alegre, Brazil.

Design and Construction of Precision Translators

J.M. Hickmann, Y.A. Folz and R.E. Francke

The implementation of different laser spectroscopic experiments demand that some components be translated or located very precisely. As an example two or more laser beams are focused onto a sample, then they have to be adjusted with a precision of the size of the focal region which is a few micrometers. This function is generally accomplished with precision translators which are generally imported and expensive due to the use of special material and high tolerance machining. In our design of a precision translator the moving part Tolls over two parallel sets of loaded spheres so that each set is held between four cylinders of M2 temper steel. Except for the spheres and cylinders, all other parts are built from 1020 carbon steel although alu- minium could have been used too. Those translators are currently been used as parts of dye laser, Michelson interferometers, Foucalt testers and others. APPENDIX -126-

PUBLICATIONS OF THE INSTITUTE OF PHYSICS

Papers published during the report period

H.O.Girotti and T.J.M.Simões: A Generalized Treatment of Point Canonical Transformations in the Path Integral, Nuovo Cimento 74E (1983) 59.

H.O.Girotti and H.J.Rothe: Quantization of Spontaneously Broken Gauge Theories in the Unitary Gauge Through the Dirac-Bracket Formalism, Nuovo Cimento 75A (1983) 62.

J.P.de Souza, E.Charry and J.W.Swart: A Very Simple Al-Gate Tech- nology for High Performance LSI Circuits, International J. of E- lectronics, 54^ (1983) 155.

P.M.Engel and J.P.de Souza: Minority Carrier Lifetime Improvement by HC1 Oxidation and Argon Ion Implantation of Silicon, J. Appl. Physics bk_ (1983) 421 1 .

C.A.dos Santos, M.Behar, J.P.de Souza and I.J.R.Baumvol: Composi- tion and Thermal Evolution of Nitrogen Implanted Steels: A Syste- matic Study, Nucl. Instr. Meth. 209 (1983) 907.

C.A.dos Santos and I.J.R.Baumvol: Nitriding of Steels: Conventio- nal Processes and Ion Implantation. In: Ion Implantation Equipment and Techniques (Springer Series in Electrophysics, vol. 11) 347-356 (1983).

L.Amaral, M.Behar, A.Maciel, L.S.de Oliveira and W.Schreiner: Structural Changes in the Switching InSe Compound Studied by TDPAC Technique, J. Phys. C: Solid State Phys. J_6 (1983) L1039.

L.G.Brunnet, M.Behar, R.Iglesias, J.A.H.da Jornada, R.P.Livi and H.Saitovitch: Temperature Dependence of the Electric Field Gradient in Agin. Interoetallic Compound, Phys. Letters 97A (1983) 294.

M.Behar, A.M.J.Perrero, A.Filevich and A.O.Macchiavelli: On the 98 98 Assignment of High-Spin CCascadea s to Rh and Pd Isotopes. Z. Phys. A 314 (1983) 111 . -127-

T.I.Morrison, P.J.Viccaro and G.K.Shenoy: Metal Ion Site Geometry and Oxidation State in Zeolites, ACS Symposium Series 218 (1983) 319.

Y.Hsu, J.E.Schmidt, M.Gupta, S.Jen, L.Berg.:r: Magnetoresistance of Pd-Fe and Pd-Ni-Fe Alloys, J. Appl. Phys. 5± (1983) 1887.

J.D.Jorgenson, D.G.Hinks, D.R.Noakes, P.J.Viccaro and G.K.Shenoy; Valence and Delocalization -of Yb in the Chevrel-Phase YbMo,S_, Phys. Rev. B27 (1983) 1465.

F.W.Kutzler, D.E.Ellis, T.I.Morrison, G.K.Shenoy and P.J.Viccaro: X-Ray Absorption Near Edge Structure in Solid Kr and KrF~, Sol. State Co mm. 4_6 (1983) 803.

G.K.Shenoy, B.Shuttler, P.J.Viccaro and D.Niarchos: Magnetic Pro- perties of Intermetallic Hydrides, J. Less Common Metals 9_4_ (1983) 37.

T.I.Morri8on, P.J.Viccaro and G.K.Shenoy: Metal Icn Site Geometry and Oxidation State in Zeolites, in Intergeolite Chemistry, eds. G.D.Stucky and F.G.Dvyer, ACS Symposium Series N9 218, p. 319, 1983.

J.B.M.da Cunha, P.J.Viccaro and A.Vasquez: A MiJssbauer Study of the Spin-Reorientation in the Pseudobinary Intermetallic Compounds (Er Gd )Fe,, Hyperfine Interactions 15/16 (1983) 697.S.

S.Jha, H.M.Seyoum, M.Demarco, G.M.Julian, D.A.Stubbs, J.W.Blue, M.T.X.Silva and A.Vasquez: Site ano Probe Dependence of Hyperfine

Magnetic Field in L21 Heusler Alloys X2MnZ (X - Ni, Cu, Rh, Pd and Z « Ga, Ge, In, Sn, Pb), Hyperfine Interactions 15/16 (1983) 697.

A.Paesano Jr., J.I.Kunrath and A.Vasquez: A Fe Mtíssbauer Study of Epidote, Hyperfine Interaction» 15/16 (1983) 841.

L.F.Ziebell and D.Dillenburg: Induced Electron-Cyclotron Emission from Inhomogeneous, Anisotropic Plasmas with Electron Population Inversion, Physics of Fluids 26_ (1983) 80. -128-

L.Amaral, F.P.Livi and A.A.Gomes: Remarks on Alloying-Induced Parameter Changes in Intermetallic Compounds, Phys. Stat. Sol. (a) 80 (1983) 669.

Alba Theumann: Second-Quantized Theory of Anderson Localization in d « 2+e, Phys. Rev. B 28 (1983) 6453.

A.R.Simões and J.R.Iglesias: Diagrammatic Method for a Mixed Va- lence Hamiltonian, J. of Magn. and Magn. Mat. 31-34 (1983) 471.

N.P.Montenegro, I.Aveline e J.R.Iglesias: Nuevo Tratamiento para el Modelo RFK, Revista Brasileira de Física J_3 (1983) 39.

E.V.Anda e J.R.Iglesias: La Actividad Cientifica en los Países De- pendientes, Rev. Mex. Fis. ^0. (1983) 119.

W.K.Theumann: First-Order Phase Transitions in the Potts Model with Trilinear Symmetry Breaking, Phys. Rev. B 27_ (1983) 6941.

W.K.Theumann: Crossover from First and Near-spinodal First-order to Continuous Transitions in the Three and Four-State Potts Model, Phys. Rev. B 2£ (1983) 6519.

M.A.Gusmão and W.K.Theumann: Validity of the Long-Range Expansion in the n-Vector Model, Phys. Rev. B 2£ (1983) 6545.

M.N.Baibich, W.B.Muir, Z.Altounian and TU-Guohua: Thermopower and Resistivity in Amorphous Cu, ,Zr Alloys, Phys. Rev. B 27 (1983) 619.

I. J .Hodgkinson, F.Horowitz, H.A.Macleod, M.Sikkens and J.J.Wharton Birefringence in Optical Coatings, J. Opt. Soc. Am., 22 (1983) 1871.

B. Buchveitz and F.L. Silveira: Entrance Examination: Comparison of Students Achievement in Four Areas of Physics, Educação e Sele- ção I (1983) 43.

M.A.Moreira and R.C.Costa: Assessment of Content and Cognitive Structures in Physics at College Level, Assessment and Evaluation in Higher Education 8_ (1983) 234. -129-

F.L.Silveira, P.H.Dionisio and B.Buchweitz: Inference about the Mean Using a Set of Data: An Aspect Related to the Sensitivity of Measurement, Ciência e Cultura 3_5 (1983) 1492.

F.L.Silveira: Considerations on the Discrimination Index of Items in Educational Tests, Educação e Seleção _7 (1983) 54.

F.L.Silveira: Discrimination Index of Psychometric Tests Items Correction, Ciincia e Cultura 35^ (1983) 78.

M.A.Moreira (ed.): University Teaching: Texts Concerning Basic Com- ponents of Instruction, Porto Alegre, Editora da Universidade, 1983, 214 p.

M.A.Moreira: A Cognitive Approach to Physics Teaching, Porto Ale- gre, Editora da Universidade, 1983, 189 p.

M.A.Moreira and C.L.Levandowski: Different Approaches to Labora- tory Teaching, Porto Alegre, Editora da Universidade, 1983, 117 p.

E.V.Anda e J,R.Iglesias: Pesquisa Científica e Desenvolvimento E- conômico na América Latina, Editora da Universidade, UFRGS, Porto Alegre, 1982; Ciincia e Cultura 3_5 (1983) 1233.

J.Schaf, K.Le Dang and P.Veillet: Spin-Glass Behaviour as a Func- tion of Concentration and Local Order by NMR in Nearly Random NiMn System, J. of Magnetism and Magnetic Materials 3_7 (1983) 297.

J.Schaf, K.Le Dang, P.Veillet and I.A.Campbell: Extended and Local Effects of Cold Working in Heusler Alloys, J. of Phys. F: Met. Phys _U (1983) 1311.

J.Schaf, K.Le Dang, P.Veillet and A.Hamzik: NMR and Magnetization Study of the Mixed Systems (Pd Cu ).MnIn and (Pd. Ni ).MnIn, 1— X Z í 1 ~X X i- J. of Magnetism and Magnetic Materials 3_6 (1983) 310.

M.G.Pastoriza, E.L.D.Bica: DDO Integrated Photometry of Globular Clusters and Initial Chemical Evolution of the Galaxy, Astrophys. and Space Science 9J_ (1983) 99.

A.Maciel, S.G.Fries, J.A.H.da Jornada, R.P.Livi and E.R.Fraga: Study of the Nuclear Quadrupole Interaction in Tl,Te., Phys. Stat. Sol. (a) 80 (1983) 245. -130-

H.A.Dottori, M.G.Pastoriza, E.L.D.Bica: DDO Photometry and Metallic Abundances of E and SO Galaxies and Globular Clusters of the LMC and SMC, Astrophysics and Space Science 8_9_ (1983) 1.

M.G.Pastoriza, U.O.RHpke: DDO Photometry on Red Giants in the Open Clusters NGC2232, NGC2287 and NGC2451, Astronomical Journal 88 (1983) 1769.

J.R.Ducati: Meio Interestelar nas Vizinhanças do Sol, Boletim da Sociedade Astronômica Brasileira, ano 6, n? 3, 1983.

M.V.F.Copetti, E.L.D.Bica: The Volumes of He+ and H+ Zones in HII Regions: The Orion Nebula, Astrophysics and Space Science 9J_ (1983) 381 .

H.A.Dottori: Bursts of Stars Formation in Detached Extragalactic HII Regions: A Qualitative Analysis, Astrophysics and Spece Science 90 (1983) 385.

P.M.Santos, N.J.Schuch, M.A.G.Maia, E.R.Vieira, H.A.Dottori, C.C. Carraro, W.C.Erick, S,C.Codina-Landaberry, F.J.von Kruger: Sítios no Brasil para Instalação de Instrumental Astronômico Rádio-Inter- ferométrico, Ciência e Cultura 3£ (1983) 1109.

S.F.Martim, R.D.Bentley, A.A.Schadee, A.Antalova, A.Kucera, L. Dezrtí, L.Gerztelyi, K.L.Harvey, H.Jones, S.H.B.Livi, J.Wang: Re- lationships of a Growing Magnetic Flux Region to Flares, Advances in Space Research 4_ (1983) 61.

S.O.Kepler, E.L.Robinson and R.E.Nather: The Light Curve of the ZZ Ceti Star G226-29, Astrophysical Journal 2JM. (1983) 744.

S.O.Kepler in B.J.Wills et al.: The QSO 1156-295: A Mult ifrequency Study of Recebt Activity, Astrophysical Journal 274 (1983) 62.

S.Balachadran, E.L.Robinson and S.O.Kepler: A Definitive Ephemerys for the 71-Second Oscillations of DQ Herculis, Publications of the Pacific Strononical Society 9_5 (1983) 653.

H.A.Dottori: 0 Efeito Sabatier e a Fotometria de Objetos Extensos, Publ. Obs. Nac. n9 1 (1983) . -131-

C.A.dos Santos, M.Behar and I.J.R.Baumvol: Surface Modifications and the Mechanical Properties of Nitrogen Implanted Carbon Steels, J. Phys. D J_7 (1984) 551 .

C.A.dos Santos, I.J.R.Baumvol, E.A.Garcia and M.Behar: Carboni- tride Precipitation by Successive Implantation of Carbon and Nitrogen into Pure Iron, J. Phys. D j_7 (1984) 969.

I.J.R.Baumvol: Ion Implantation Metallurgy. School Book for the Fourth International School on Ion Implantation Equipment and Techniques, Pergamon Press, New York (1984) p. 261.

M.Behar, J.P.Bier sack , P.F.P.Fichtner, D.Fink, C.V.de B.Leite Fi- lho, C .A.01ivieri, B.K.Patnaik, J.P.de Souza and F.C.Zawislak: Range and Range Straggling of 15 to 350 keV Ga in Amorphous Silicon, Rad. Effects Letters 85 (1984) 117.

L.Amaral, M.Behar, A.Maciel and H.Saitovitch: Anomalous Tempera- ture Behaviour of the Electric Field Gradient in the InSe Semi- conductor Compound, Phys. Lett. 102 A (1984) 45.

M.A.J.Mariscotti, A.J.Kreiner, M.Behar, A.O.Machiavel1i, G.Garcia Bermudez, A.M.J.Ferrero, C.Backtaski and P.Thieberger: The High Spin-Structure of 100Rh, Nucl. Phys. A 243 (1984) 167.

Rejane M.Ribeiro-Teixeira, M.H.Preis Corrêa, A.Vasquez and C.E.T. Gonçalves da Silva: Hyperfine Magnetic Fields in (Pd,Au).Fe, Physica 124B (1984) 218.

L.Amaral, F.P.Livi and A.A.Gomes: A Model for the E.Q.I, in High d-Density of States Metallic Systems, An. Acad. Brasil. Ciênc. _56(1) (1984).

L.F.Ziebell and D.Dillenburg: Momentum Distribution Dependence of Induced Electron-Cyclotron Emission, Revista Brasileira de Física, vol. 13, n9 4 (1984).

G.L.F.Fraga, J.V.Kunzler, F.Ogíba and D.E.Brandão: Electrical

Resistivity of the Ni2MnIn Heusler Alloy, Phys. Stat. Sol. (a) 83 (1984) K187. -132-

S.T.Tsai, M.Tanaka, J.D.Gaffey Jr., E.H.da Jornada, C.S.Wu and L.F.Ziebell: Effect of Electron Thermal Anisotropy on the Kinetic Cross-Field Streaming Instability, J. Plasma Physics J_2. (1984) 159.

J.E.Schmidt and L.Berger: Magnetostriction of Pd-Fe Alloys, J. Appl. Phys. 5j[ (1984) 1073.

E.A.Veit, B.K.Jennings, R.C.Barrett and A.W.Thomas: Kaon-Nucleon Scattering in an Extended Cloudy Bag Model, Phys. Lett. 137B (1984) 415.

B.K.Jennings, E.A.Veit and A.W.Thomas: Pion-Nucleon Scattering Lengths in the Cloudy Bag Model, Phys. Lett. 148B (1984) 28.

M.Dillig, V.E.Herscovitz and M.R.Teodoro: e-Hypernuclear Low-Lying States in 1^C, J. Phys. G: Nucl. Phys. j_0 (1984) L59. La 'm^~~~

Alba Theumann and M.T.Béal-Monod: Singularities in the Paramagne- tism of Two-Dimensional Nearly Magnetic Itinerant-Fermion Systems at Very Low Temperature: Application to Degenerate Two-Dimensional Liquid-3He Films, Phys. Rev. B 2_9 (1984) 2567.

Alba Theumann and Mercedes Vieira Gusmão: Quantum Ising Spin-Glass, Phys. Lett. 105A (1984) 311.

A.R.Simões, J.R.Iglesías and E.V.Anda: Green Function Method for a Mixed Valence Hamiltonian, Phys. Rev. B29 (1984) 3085.

J.R. Iglesias: Ciência Dependente, Editora da Universidade, UFRGS, Porto Alegre, 1983; Ciência e Cultura, 3^6 (1984) 966.

A.Latgé, R.Ribeiro-Teixeira and J.R.Iglesias: Binding Energy of a Hydrogen Impurity in an f.c.c. Lattice, Solid State Comm. , _5_2_ (1984) 87.

M.Betz, G.Krein and Th.A.J.Maris: Bags in the Shell Model, Nuclear Physics A437 (1984) 509.

W.K.Theumann and M.A.Gusmão: Crossover Exponents for the Potts Model with Quadratic Symmetry Breaking, Phys. Rev. B 3J) (1984) 2800. -133-

M.A.Moreira: Concept Maps as Instruments for Learning Evaluation, Educação e Seleção J_0 (1984) 17.

B.Buchweitz and M.H.S.Motta: Double Evaluation of Essays: Comparing Scores, Educação e Seleção J[0 (1984) 83.

F.L.Silveira and M.A.Moreira: Student Evaluation of Teacher's Performance: Evidences of Validity of an Instrument, Ciência e Cultura 3_6 (1984) 466.

M.A.Moreira and R.V.A.Baquero: Improving University Teaching: Supporting Small Projects as a Strategy for Instructional Develop- ment, Ciência e Cultura 3_6 (1984) 737.

F.L.Silveira and J.C.Gaspar in: Measuring Attitude Towards the Laboratory in Introductory College Physics, Educação e Seleção 9 (1984) 65.

B.Buchweitz: The Use of Concept Maps in the Analysis of Curriculum, Educação e Seleção j_0 (1984) 3.

C.A.dos Santos and M.A.Moreira : Cognitive Mapping in Thermodynamics Through Multidimensional Scaling, Revista Contactos, Mexico, 1984.

B.Buchweitz et allii: Analysis of Items of the Entrance Examination of the UFRGS-1984, Porto Alegre, Editora da Universidade/COPERSO, 1984, 279 p.

T.S.Bergmann, S.H.B.Livi, R.D.D.Costa: BV and DDO Photometric Observations of Red Variable Stars, Astrophysics and Space Science 100 (1984) 341. ^—^— i i S.O.Kepler: The ZZ Ceti Star GD 385 Revisited, Astrophysical Journal ^7_8 (1984) 754.

D.E.Winget, R.E.Nattier and S.O.Képler: PG 1116+158, IAU Circular n9 3932, 1984.

i J.E.Solheim, E.L.Robinson, R.E.Nattier and S.O.Kepler: The 1051 s Period of the Interacting Binary White Dwarf AM CVn, Astronomy and Astrophysics 135 (1984) 1. -134-

S.O.Kepler: Light and Line Profile Variations Due to r-Mode Pul- sations, with an Application to the ZZ Ceti Star G117-B15A, Astro- physical Journal 286 (198A) 314.

M.V.F.Copetti, H.A.Dottori, E.L.A.Bica, M.G.Pastoriza: Age Deter- mination of H II Regions of the LMC and SMC, Proc. IAU Symp. 108, S. van den Bergh and K.S. de Boer, eds., p. 383 (1984). -135-

Papers accepted for publication

H.O.Girotti and K.D.Rothe: Quantization of QED and QCD in a Fully Fixed Temporal Gauge. Zeitschrift für Physik C.

M.Behar, P.F.P.Fichtner, C.A.01ivieri, J.P.de Souza, F.C.Zawislak, J.P.Biersack, D.Fink and M.StMdele: Range Profiles of 10 to 380 keV 120 133 Sn and Cs in Amorphous Silicon. Radiation Effects.

P.H.Dionisio, B.A.S.de Barros Jr. and I.J.R.Baumvol: Interne tal1ic Phases Formed During Tin Implantation into Iron and Steels. J. of Applied Physics.

M.Behar, P.F.P.Fichtner, C.A.Olivieri, J.P.de Souza, F.C.Zawislak and J.P.Biersack: Range Profiles of Implanted Bi and Au in Amor- phous Silicon. Nucl, Instr. and Methods, section B.

C.A.Olivieri, M.Behar, P.F.P.Fichtner, F.C.Zawislak, D.Fink and J.P.Biersack: Depth Profile and Thermal Annealing Behaviour of Bi Implanted into an Al/Ti Bilayer Structure. J. Appl. Physics.

C.R.Wie, C.R.Shi, M.H.Mendenhall, R.P.Livi, T.Vreeland Jr. and T.A.Tombrello: Two Types of MeV Ion Beam Enhanced Adhesion for Au Films on SiO». Nucl. Instr. and Methods.

P.M.Mors, A.S.R.Simões, J.R.Iglesias and E.V.Anda: Real Space Re- normalization of a Mixed Valence Hamiltonian on a Bethe Lattice. Solid State Comm.

P.M.Mors and J.R.Iglesias: Effect of the d-f Coulomb Correlation on the Valence Transition of Intermediate Valence Systems. Solid State Comm.

W.K.Theumann and M.A.Gu»mão: Critical Exponents for <|>3-Field Mo- dels with Long-Range Interactions. Phys. Review B.

E.H.da Jornada, J.D.Gaffey, Jr., and D.Winske: Instabilities Excited by an Energetic Ion Beam and Electronic Temperature Ani- sotropy in Tandem Mirrors. Physics of Fluids. -136-

A.M.Umarji, D.R.Noakes, P.J.Viccaro, G.K.Shenoy. A.T.Aldred and D.Niarchos: Magnetic Properties of REFe_Si_ Compounds. J. Mag. and Mag. Materials.

M.H.Preis Corria, W.H.Schreiner, J.E.Schmidt, P.J.Viccaro and A.Vasquez: Magnetic Properties of the Hydride Pd-FeH_ ,. J. of Phys. F: Metal Physics.

J.B.M.da Cunha, P.J.Viccaro and A.Vasquez: Spin Reorientation in (Er.Gd)Fe- Compounds. J. Phys. F: Metal Physics.

S.Jha, K.M.Seyoum, G.M.Julian, R.A.Dunlap, A.Vasquez, J.B.M.da Cunha and A.Vasquez: Hyperfine Fields at sp Sites in the Heusler Alloys Rh-MnZ (Z - Ge, Sn, Pb). Phys. Rev. Brief Reports.

H.P.Freund, P.Sprangle, D.Dillenburg, E.H.da Jornada, B.Liberman and R.S.Schneider: The Effect of an Axial Guide Field on Free Electron Lasers. Physics of Quantum Electronics, ed. Addison Wesley.

M.Sikkens, I.J.Hodgkinson, F.Horowitz, H.A.Macleod and J.J.Whar- ton: Computer Simulation of Thin Film Growth: Applying the Results to Optical Coatings. SPIE Proceedings.

M.R.Jacob son, F.Horowitz and B.Liao: Deposition Characterization and Simulation of THin Films with Form Birefringence. SPIE Pro- ceedings .

P.Kitching, W.J.McDonald, Th.A.J.Maris and C.A.Z.Vasconcellos: Recent Developments in Quasi-Free Nucleon-Nucleon Scattering. Advances in Nuclear Physics.

M.Betz: Center-of-Mass and Recoil Corrections in Bag Models. Re- vista Brasileira de Física, Volume Especial, Física de Energias Intermediárias.

M.A.Moreira; Concept Mapping: An Alternative Strategy for Evalua- tion. Assessment and Evaluation in Higher Education.

M.A.Moreira: Methodology of Research and Methodology of Teaching: A Practical Application. Ciência e Cultura. -137-

F.L.Silveira et allii: Student Evaluation of Teacher's Perfor- mance: New Evidences of Validity of an Instrument. Ciência e Cultura.

R.Axt and V.H.Guimarães: Experimental Physics Teaching in Secon- dary Schools: An Attempt to Make it Feasible. Ciência e Cultura.

R.Axt: Intuitive Concepts in Objective Items Applied in Entrance Examinations at the Universidade Federal do Rio Grande do Sul. Ciência e Cultura.

M.A.Moreira: Teaching and Learning: Theoretical Approaches. Editora Moraes, São Paulo, Brazil.

W.H.Schreiner, W.Stamm and E.F.Wasserraann: Magnetic Properties of the Mixed System Pt (Mn.Fe) . J. Phys. F: Metal Phys.

M.H.Steffani, M.Betz e Th.A.J.Mar is: Tempo de Vida de Estados de Buraco Nucleares num Modelo de Teoria de Campos. Revista Brasi- leira de Física, Volume Especial, Física de Energias Intermediá- rias.

C.A.Z.Vasconcellos, C.Schreiner e Th.A.J.Maris: Polarização Efeti- va em Espalhamento Quase-Livre e Estrutura Nuclear. Revista Brasi- leira de Física, Volume Especial, Física de Energias Intermediá- rias.

M.A.Z.Vasconcellos e M.N.Baibich: Cristalização de Ligas Amorfas

Pseudobinárias Tipo (Fe, Ni )o.Bon. First Latin American Sympo- 1 —X X SU ZU síum on Amorphous Systems Physics, Suplement of Revista Brasilei- ra de Física. M.A.Z.Vasconcellos , P.F.P.Fichtner, R.P.Livi, F.P.Livi, M.I.da Costa Jr. e M.N.Baibich: Magnetismo Macroscópico e Microscópico de Ligas Amorfas Tipo Metal-Metalóide. Annals of the First Latin American Symposium on Amorphous Systems Physics, Suplement of Re- vista Brasileira de Física

M.N.Baibich: Idéias e Resultados de Transporte Eletrônico em Me- tais Amorfos. Annals of the First Latin American Symposium on A- morphous Systems Physics, Supl;ment of Revista Brasileira de Fí- sica . -138-

M.N.Baibich: Os Modelos de Metal Líquido Aplicados aos Vidros Me- tálicos. Annals of the First Latin American Symposium on Amorphous Systems Physics, Suplement of Revista Brasileira de Física.

M.N.Baibich: Os Modelos Tipo Kondo Aplicados aos Metais Amorfos. Annals of the First Latin American Symposium on Amorphous Systems Physics, Suplement of Revista Brasileira de Física.

M.N.Baibich: Contribuição do Zr para o Transporte Eletrônico do Cu Zr Amorfo. Annals of the First Latin American Symposium on Amorphous Systems Physics, Suplement of Revista Brasileira de Fís.

M.N.Baibich: Formação de Vidros Metálicos. Annals of the First La- tin American Symposium on Amorphous Systems Physics, Suplement of Revista Brasileira de Física.

G.Krein: Quarks e o Modelo de Camadas, Revista Brasileira de Físi- ca, Volume Especial, Física de Energias Intermediárias.

M.Behar, A.M.J.Ferrero, A.Filevich and A.0.Macchiavelli: High Spin 97 States in Rh, Z. Phys. A - Atoms and Nuclei.

D.Fink, J.P.Biersack, J.T.Cha, S.Klarminzar, W.Schnabel, M.StHdele, K.Tjan, M.Behar, C.A.Olivieri and F.C.Zavislak: Distribution of Light Ions and Foil Destruction after Irradiation of Organic Poly- mers, J. of Applied Physics. -139-

PAPERS PRESENTED AT MEETINGS AND CONFERENCES

International Meetings and Conferences

Y_L !international Conference on Hyperfine Interactions, Groeningen, Holland, 1983

M.Behar, L.G.Brunnet, J.A.H.da Jornada, R.P.Livi and F.C.Zawislak Temperature Dependence of the EFG in the Agin. Hyperfine Interactions 15/16 (1983) 261

J.B.M.da Cunha, P.J.Viccaro and A.Vasquez A MfJssbauer Study of the Spin-Reorientation in the Pseudo-Binary Intermetallic Compounds (Er Gd )Fe.

S.Jha, H.M.Seyoum, M.Demarco, G.M.Julian, D.A.Stubbs, J.W.Blue, M.T.X.Silva and A.Vasquez Site and Probe Dependence of Hyperfine Magnetic Field in L2.

Heusler Alloys X2MnZ (X - Ni, Cu, Rh, Pd and Z - Ga, Ge, In, Sn, Pb)

Congress o_f_ the Canadian Association of Physicist, Victoria, Canada

E.A.Veit and B.K.Jennings The KN Scattering and the CBM Bulletin of Canad. Assoc. of Physicist, Vol. 39, n° 3, Congress Issue, 1983, p. 57 (DJ3)

10th International Conference on Few Body Problems jit» Physics, KacJ sruhe, W.Germany, August 1983

E.A.Veit, B.K.Jennings and R.C.Barret The KN Scattering and the Cloudy Bag Model

R.C.Barret, B.K.Jennings, E.A.Veit and A.U.Thomas Kaon Scattering and the Cloudy Bag Model -140-

Los Alamos Conference on Op tics, Los Alamos, New Mexico, April 1983

F.Horowitz and H.A.Macleod Form Birefringence in Thin Films

Opt ical Society oi_ America Annual Meeting, New Orleans, Louisiana, October 1983

I.J.Hodgkinson, F.Horowitz, H.A.Macleod, M.Sikkens and J.J.Wharton Birefringence in Optical Coatings

Fifteenth IUPAP International Conference on Thermodynamics and Statistical Mechanics, July 25-29, 1983, University oi^ Edinburgh

W.K.Theumann First and Second-order Phase Transitions in the Potts Model with Quadratic and Trilinear Symmetry Breaking

International Summer Workshop on Physics Education, La Londe Les Maures, France, June 26-July 13, 1983

M.A.Moreira and G.W.Ahumada Concept Maps and Tools to Investigate Cognitive Structure in Physics

International Seminar on Physics Educat ion, Caracas, Venezuela, August 1983

M.A.Moreira and G.W.Ahumada Concept Maps ai Tools for Evaluation in Physics Teaching

M.A.Moreira and S.T.Gobara Concept Maps as Instructional Tools in Physics Teaching

Third National Meeting oji Physics Education, Cordoba, Argentina, October 1983

M.A.Moreira Concept Maps in Physics Teaching -141-

International Conference on Nuclear Physics, Florence, Italy, August 29-September 3, 1983

M.Dillig, V.E.Herscovitz and M.R.Teodoro — 13 Excitation of Low-Spin (AN) States in C(p,d) Published in the Proceedings of the Conference

University of Alberta/TRIUMF Workshop, Studying Nuclei with Medium Energy Protons, Edmonton, Alberta, Canada, July 11-13, 1983

M.Dillig, V.E.Herscovitz and M.R.Teodoro A-Isobar Effects in Quasi-Free Scattering

International Astronomy Union Symposium n_9_ 108, Heidelberg, RFA, 1983

M.V.F.Copetti, H.A.Dottori, E.L.A.Bica, M.G.Pastoriza Age Determinations of HII Regions of the LMC and SMC

III Delaware Workshop on White Stars, USA, 1983

S.O.Kepler The Light Curves of the ZZ Ceti Stars G226-29

III Regional Latin American Astronomy Meeting, Buenos Aires, Argentina, 26-30 November, 1983

J.R.Ducati Distribuição da Extinção Interestelar nas Vizinhanças do Sol

M.V.F.Copetti, H.A.Dottori, M.G.Pastoriza Indicadores de Edad de Regiones HII * S.M.Bisch, M.G.Pastoriza, I.Burko, H.A.Dottori UBV Variations in the Seyfert Galaxies K4329A, NGC7469 and NGC6814

T.S.Bergmann and M.F.S.Schroeder Surface Photometry of Southern Galaxies -142-

M.G.Pastoriza, H.A.Dottori Espectro de Absorcion, Continuo Óptico y Enrojecimento en Núcleos Normales y Activos de Galáxias

Applications of Accelerators rn the Interdisciplinary yields, Padova, Italy, May 1984

D.Fink, M.Behar, J.P.Biersack, H.D.Carstanjen, M.StMdele and F.C. Zawislak Complementary Use of Nuclear Reaction Analysis with Thermal Neutrons and Conventional Ion Beam Techniques for Space Technology

Symposium Three Day in Depth-Review on Nuclear Accelerator Impact in the Interdisciplinary Field, Padova, Italy, May 30-June 1st, 1984

Rogério P.Livi, Marcus H.Mendenhall, T.A.Tombrello, Gerald Fine and Edward Stolper High Sensitivity Carbon Content Analysis of Geological Materials Using 1.4 MeV Deuterons To be published in Nuclear Instruments and Methods B

Marcus Mendenhall, Rogério P.Livi and T.A.Tombrello Heavy Ion Rutherford Scattering for Measurement of Heavy Element Concentrations and Isotopic Ratios To be published in Nuclear Instruments and Methods B

Eighth Conference on the Application o_f_ Accelerators in Research and Industry, Denton, Texas, 12-14 November, 1984

R.P.Livi Adhesion Enhancement Induced by MeV Ion Beams To be published in Nuclear Instruments and Methods -143-

Congress c>f_ the Canadian Association o_f_ Physicist, Sherbrooke, Canada, June 198A

E.A.Veit, B.K.Jennings and A.W.Thomas The KN Scattering Length in the CBM Bull, of Canad. Assoc. of Physicist, vol. 40, n9 3, Congress Issue, 1984, p 36 (PE5)

4th International Conference o_n Clustering Aspect o_f Nuclear Structure and Nuclear Reactions, Chester, England, July 1984

R.C.Barret, B.K.Jennings, E.A.Veit and A.W.Thomas CBM Prediction for the KN Interaction and Kaonic Hydrogen Preprint university of Adelaide, ADP 287, June 1984

10th International Conference on Particles and Nuclei, Heidelberg, W.Germany, July 1984

E.A.Veit, B.K.Jennings and A.W.Thomas KN Scattering in the Cloudy Bag Model Proceed, of the Conference, Heidelberg, 30/7-3/8, 1984. Book of Abstracts, vol. II, p M16

A.W.Thomas, E.A.Veit and A.W.Thomas TT-N s-Wave Scattering Length in the Cloudy Bag Model Proceed, of the Conference, Heidelberg, 30/7-3/8, 1984. Book of Abstracts, vol. I, p B23

E.A.Veit, B.K.Jennings, R.C.Barret and A.W.Thomas On the Nature of the A*(1405) Proceed, of the Conference, Heidelberg, 30/7-3/8, 1984. Book of Abstract», vol. II, p M19

1984 SPIE Conference, San Diego, California, August

M.Sikkens, I.J.Hodgkinson, F.Horowitz, H.A.Macleod and J.J.Wharton Computer Simulation of Thin Film Growth: Applying the Results to Optical Coatings -144-

M.R.Jacobson, F.Horowitz and B.Liao Deposition, Characterization and Simulation of Thin Films vith Fora Birefringence

Fall Meeting of the Materials Research Society, Boston, Massachu- setts, November 1984

R.P.Livi, S.Paine, C.R.Wie, M.H.Mendenhall, J.Y.Tane, T.Vreeland Jr. and T.A.Tombrello Electrical Contact and Adhesion Modification Produced by High Energy Heavy Ion Bombardment of Au Films on GdAs To be published in the Proceedings of the Conference

Topical Meeting ojn Optical Interference Coatings, 1984 Spring Con- ference on Applied Optics, Monterey, Cal ifornia, April 1984

I.J.Hodgkinson, F.Horowitz, H.A.Macleod, M.Sikkens and J.J.Wharton Structural Effects in Thin Film Coatings

Physics Meeting gn Condensed Matter, Münster, W.Germany, 1984

W.H.Schreiner, W.Stamm and E.F.Wassermann Magnetic Properties in the System Pt-(Mn.Fe)

Workshop on Local and Global Methods o_f Dynamics, Naval Surface Weapons Laboratory, Silver Springs, Maryland, July 23-26, 1984

J.Goedert and H.Ralph Lewis Exact Invariants in the Form of Momentum Resonances for Particle Motion in One-Dimensional, Time-Dependent Potentials

AGU Meeting, Cincinnati, May 14-18, 1984

J.D.Gaffey Jr., E.H.da Jornada and D.Winske Instabilities due to Transmitted and Reflected Ions and Electron Temperature Anisotropy in the Quasi-Perpendicular Bow Shock -145-

Sherwood Theory Meeting, Nevada, April 11-13, 1984

J.D.Gaffey Jr., E.H.da Jornada and D.Winske Instabilities Excited by an Energetic Ion Beam and Electron Tem- perature Anisotropy in Tandem Mirror

International School on _Ion Implantation Science and Technology, Burlington, Vermont, USA, 1984

Israel Baumvol Ion Implantation Metallurgy

International Astronomy Union Colloquy N9 81, The Local Inter- stellar Medium, Madison, USA, June 4-6, 1984

J.R.Ducat i The Distribution of Interstellar Extinction Near the Sun

IV Regional Latin American Astronomy Meeting, Rio de Janeiro, November 19-24, 1984

T.S.Bergmann and M.F.S.Schroeder Fotometria Fotográfica Superficial BV de Galáxias Austrais

S.M.Birch, H.A.Dottori, I.Burko Análise de Variabilidade UBV em Núcleos de Galáxias Seyfert

H.A.Dottori, C.Bonatto Análise de Variabilidade de NGC3783

M.V.F.Copetti, H.A.Dottori

Determinação Fotométrica de Wu e [0III]/H em Regiões de M83 H

i H.A.Dottori, M.V.F.Copetti Determinação de Idades de Regiões HII Galácticas

i H.A.Dottori Observações Espectrofotométricas de Núcleos de Galáxias

H.A.Dottori Morfology of Globular Clusters of the LMC -146-

D.E.Winget e S.O.Kepler Taxa de Evolução da Pré-Anã Branca PG1159-035

S.O.Kepler Pulsações das Estrelas ZZ Ceti

XXX Conference on Magnetism and Magnetic Materials, San Diego, USA, November 1984

S.P.da Cryz and F.P.Livi Inductive Observation of Transitions from [100] Magnetic Domains to [010] and [001] in Silicon-Iron

I_V Japan-Brazil Symposium on Science and Technology, São Paulo and Rio de Janeiro, 1984

L.F.Ziebel and D.Dillenburg Wave Absorption by Fast Electrons with Non-Maxwel1ian Perpendi- cular Momentum Distribution Volume III, 1984, p. 150 a 161

— Latin American Symposium oil Amorphous Systems Physics, Niterói, RJ, February 1984

M.A.Z.Vasconcellos e M.N.Baibich

Cristalização de Ligas Amorfas Pseudo-Binárias Tipo (Fe. Ni )QnBor. I—X X OU i\i M.A.Z.Vasconcellos et allii Magnetismo Macroscópico e Microscópico de Ligas Amorfas tipo Metal-Metalóide

M.N.Baibich Contribuição do Zr para o Transporte Eletrônico do Cu Zr Amorfo

Ion Beam Modification £f Materials, Cornell, USA, 1984

R.Erichsen Jr., J.P.de Souza and I.J.R.Baumvol Recoil Implantation of Antimony into Silicon by Argon Ion Bombardment To be published in Nuclear Instruments and Methods B -147-

M.Deicher, G.Grübel, E.Recknagel, Th.Winchert and M.Behar In-Impurity Interactions in Defect Cascades

National Meetings and Conferences

IV National Meeting on Particles and Fields Physics, Itatiaia, Brazil, September, 1983

M.E.V.Costa, H.O.Girotti e T.J.Simões Reinterpretação da Formulação Lagrangeana dos Sistemas Vinculados

V.E.Herscovitz, M.R.Teodoro e M.Dillig Àcoplamentos Quark-Meson e Barion-Meson

V.E.Herscovitz, M.R.Teodoro e M.Dillig Formulação de Campo Médio Relativístico para Sistemas Bariônicos ri National Meeting on MHssbauer Spectroscopy, Belo Horizonte, MG, 1983

J.B.M.da Cunha, P.J.Viccaro e A.Vasquez Estudo da Anisotropia Magnética nos Compostos Intermetálicos

Pseudobinários (Er1 G4 )Fe_ por Espectroscopia Müssbauer no Fe

M.H.Preis Corrêa, W.H.Schreiner, J.E.Schmidt, P.J.Viccaro e A.Vasquez Propriedades Magnéticas da Liga de Pd.Fe Ordenada c Hidrogtnada -148-

L.Zavislak, P.J.Viccaro, H.H.Preis Corrêa e A.Vasquez Estudo do Processo de Ordenamento em Pd.Fe

Carlos A.dos Santos, Hermes A.Pacheco, P.J.Viccaro e A.Vasquez Transformações na Tantalita-Columbita a Altas Temperaturas

_y_I National Meeting on Condensed Matter Physics, São Lourenço, MG, May 4-7, 1983

W.K.Theumann Transições de Fase no Modelo de Potts com Quebra de Simetria

Miguel Gusmão e W.K.Theumann Expoentes Críticos do Modelo Vectorial com Interações de Longo Alcance

Workshop on Phase Trans i t ions in Statistical Mechanics and Quantum Theory o_f_ Fields, IFUSP, December 5-9, 1983

W.K.Theumann Transições de Fase Contínuas Induzidas por Flutuações no Modelo de Pctts

XXXV Annual Meet ing of the Brazilian Soc iety for the Advancement o_f Science, Belém, PA, 1983

G.L.Fraga, J.V.Kunzler e D.E.Brandão Estudo da Resistividade Elétrica de Ligas de Heusler Ferromagné- ticas do Tipo Ni.Mndn. Sn ) em Função da Temperatura e da Con- fc I ^X X centração

G.L.Fraga, J.V.Kunzler, D.E.Brandão, F.Ogiba, W.H.Schreiner Estudo do Mecanismo de Espalhamento Magnético Eletrônico nas Ligas de Heusler Ni-Mnln e Ni^MnSn

M.A.Z.Vasconcellos, P.F.P.Fichtner, R.P.Livi, F.P.Liví, M.I.da Costa Jr. e M.N.Baíbich

Magnetismo de Ligas Amorfas Pseudobinárías do Tipo (Fe,. .Ni )ínB,n -149-

M.N.Baibich Dependência do Poder Termoelétrico de Ligas Amorfas Tipo Cu ^Zr com Dependência em Energia do Pseudopotencial

K.I.Kunrath e Adalberto Vasquez Efeito Müssbauer: Técnica Seletiva de Identificação de Impurezas de Baixa Concentração

Livio Amaral, Flavio P.Livi e Adalberto Vasquez Investigação por Espectroscopia Müssbauer da Série Zr(Fe,Si)_

L.M.A.Diehl, E.Mattievich, M.Terezinha X.Silva e Adalberto Vasquez Ferromagnetismo Fraco na Série Isoestrutural Fosfof errita-Krizha- novski ta

A.Maciel, S.G.Fries, J.A.H.da Jornada e E.R.Fraga Dependência com a Temperatura da Interação Quadripolar Elétrica do Cd no Composto Tl,.Te_

S.G.Fries, A.Maciel e J.A.H.da Jornada Efeito da Pressão sobre o Gradiente de Campo Elétrico (G.C.E.) no

Composto Interne talico In2Bi

L.S.de Oliveira, J.Belanca, J.A.H.da Jornada Câmara Tipo Pistão Cilindro para Processamento de Materiais com Temperatura

Y.A.Folz, Luci F.Motter, J.F.dos Santos, R.E.Francke e H.A.Dottori Construção de uma Câmara de Alto Vácuo para a Deposição de Filmes Finos

J.A.Lisboa, T.Braun e R.E.Francke

Inomogeneidades Espacial e Temporal no Ganho do Laser de N?

Annual Meeting of the Brazilian Astronomical Society, Itajuba, MG, Brasil, July 27-30 1983

H.A.Dottori Estudo Comparativo de Núcleos de Galáxias Espirais Normais, Pe- culiares e Seyferts -150-

H.A.Dottori Aplicação de um Método de Programação não Linear à Síntese de Espectros de Absorção Compostos

M.V.F.Copetti, H.A.Dottori, M.G.Pastoriza Evolução de Regiões HII

J.R.Ducati Amplicidade Estelar e Fotometria nvbyB

K.RÜpke e M.G.Pas toriza Resultados do Estudo Fotométrico BV-DDO de Gigantes Vermelhas nos Aglomerados Abertos NGC2232, NGC2281, NGC2451, NGC5460, NGC6087 e NGC6287

M.G.Pastoriza, T.S.Bergmann e A.Schmidt Fotometria BV-DDO de Estrelas G e K y_ Nac ional Meet ing an Part ic les and Fields Physics , Itatiaia , RJ , September, 1984

J.J.M.Simões e H.O.Girotti Quantização Operatorial das Teorias de Gauge Não-Abelianas

III National Meet ing o_n Mflssbauer Spectroscopy, São Paulo, SP, 1984

P.J.Viccaro Absorção de Hidrogênio em Metais e Ligas

M.T.X.Silva, J.Schaf, A.Vasquez e P.J.Viccaro Efeitos de Oxídação Medidos por CEMS na Liga Fe-V

S.M.M.Ramos, J.B.M.Cunha, A.Vasquez e S.Jha Estudo Sistemático dos Campos Hiperfinos em Ligas de Heusler do 119 Tipo RhjYZ com Impureza de Sn por Espectroscopia MBssbauer -151-

VII National Meeting on Condensed Matter Physics, São Lourenço, MG, Ma£ lzl> 1984

F.Horowitz Thin Films for Optical Applications

W.K.Theumann e M.Â.Gusmão Expoentes de Crossover do Modelo de Potts com Quebra de Simetria Quadrãtica

Mareia Barbosa e W.K.Theumann Renormalizabilidade do Modelo de Potts com Quebra de Simetria Quadrática

M.A.Gusmão e W.K.Theumann Expoentes Críticos do Modelo de Potts com Interações de Longo Alcance

W.K.Theumann Continuidade e Descontinuidade dos Expoentes Críticos do Modelo de Potts com Interações de Longo Alcance

II Workshop on Statistical Mechanics and Theory o_f_ Fields, USP, São Carlos, December 12-15, 1984

Mareia C.Barbosa, José F.Fontanari, M.A.Gusmão and W.K.Theumann Renormalização do Modelo de Potts com Quebra de Simatria: Tran- sição no SrTiO-

XXXVI Annual Meeting of the Brazilian Society for the Advancement £f_ Science, São Paulo, July 1984

S.T.Gabara and M.A.Moreira Concept Mapping as a Didactical Aid in Physics Teaching

F.L.Silveira, M.A.Moreira and A.D.Nunes Evaluation of the Physics Teacher Performance Through Students Opinion

F.L.Silveira and J.C.Gasparin Measuring Student's Attitude Towards Laboratory Physics Instruction. -152-

Y.A.Folz, L.F.Motter, H.A.Dottori, F.Horowitz e R.E.Francke Fontes de Grafite para Evaporação Térmica de Alumínio

C.Schoneweg, L.F.Motter, F.Horowitz e R.E.Francke Lente de Fresnel para Retroprojetor

M.I.da Costa Jr., M.A.Z.Vasconcellos, J.V.Kunzler e M.N.Baibich Propriedades da Fase Heusler Pura da Liga Cu.MnSn

G.L.F.Fraga, J.V.Kunzler e D.E.Brandão Estudo da Resistividade Elétrica de Ligas de Heusler Pseudo-Ter nárias Ferromagnéticas do Tipo Ni-Mn(Sn. In ) em Função da Tem peratura

M.N.Baibich, M.A.P.Idiart, G.Weissmüller e J.E.Schmidt

Elasticidade de Fitas Metálicas Amorfas Tipo (FeNi)8QB20

J.E.Schmidt, M.A.Z.Vasconcellos, M.A.P.Idiart, W.H.Schreiner e M.N.Baibich Magnetostricçao de Ligas Amorfas Pseudobinárias Tipo

M.Fin e M.N.Baibich Medidor de Temperatura para Sensores Resistivos a Baixas Tempera- turas

M.Fin e M.N.Baibich Compensador Confiável de Temperatura Ambiente para Termopares

M.Fin e M.N.Baibich Servo-Controle Proporcional para Forno Resistivo

J.E.Schmidt, J.B.M.da Cunha e P.J.Viccaro Efeitos de Reoríentação de Spin na Magnetostricçao Linear do ErFe»

J.I.Kunrath, J.B.M.da Cunha Interação Hiperfina em Silicato Duplo pela Técnica Mb**»bauer -153-

V National Meeting on Intermediate Energy Physics, Gramado, RS, May 7-9, 1984

Th.A.J.Mar is 0 Modelo de Camadas e o Modelo de Sacola

M.Betz Center-of-Mass and Recoil Corrections in Bag Models

M.H.Steffani, M.Betz e Th.A.J.Maris Tempo de Vida de Estados de Buraco Nucleares num Modelo de Teoria de Campos

C.A.Z.Vasconcellos, C.Schneider e Th.A.J.Maris Polarização Efetiva em Espalhamento Quase-Livre e Estrutura Nuclear

G.Krein Quarks e o Modelo de Camadas

V.E .Herscovítz, M.R.Teodoro and M.Dillig Repulsão de Curto Alcance em Interações Barionicas e Abordagem Relativística Simplificada

Workshop ££ Nuclear Physics, Itatiaia, SP, September 1984

G.Krein e Th.A.J.Maris 0 Modelo de Camadas e o Bag Model

M.Betz Movimento de Centro de Massa no Modelo de Sacola

Perspective» of_ the Nuclear Physics ij± Brasil» São Paulo, SP, November 1984

Th.A.J.Maris Sacolas em Camadas? -154-

Annual Meeting of the Brazilian Astronomical Society, Sao Paulo, £P, July 5-7, 1984

M.V.F.Copetti, H.A.Dottori, M.Pastoriza, J.Melnick Determinação de Idade de Regiões HII Galácticas

T.S.Bergmann, M.G.Pastoriza e M.F.S.Schroeder Fotometria Superficial BV das Galáxias NGC6769, 6770, 6771

H.S.Dottori, M.G.Pastoriza e J.F.dos Santos Jr. Espectro de Absorção Estelar no Núcleo Peculiar de NGC7552

H.A.Dottori e A.Zepka Elipticidade de Aglomerados Globulares na Grande Nuvem de Magalhães -155-

M.Sc. THESES - 1983 and 1984

Waldo Ahumada Guerra - Jan. 25, 1983 Mapas Conceituais como Instrumentos para Investigar a Estrutura Cognitiva em Física

Antonio Vicente Lima Porto - March 1st, 1983 Atividades Experimentais para o Ensino de Mecânica de Fluidos em Nível Universitário Básico

Ursula Olga Rflpke - March 15, 1983 Estudo Fotométrico de Gigantes Vermelhas em Aglomerados Abertos

Tarso Fernando Cassol - March 18, 1983 Aproximação de Campo de Reação para Hamiltoniano de Heisenberg em Sistemas de Duas Redes Não-Equivalentes de Spins

Leonardo Gregory Brunnet - April 5, 1983 Efeito de Temperatura e Pressão na Interação Quadrupolar Elétrica em Agln~

Paulo Cesar Tettamanzy D'Ajello - April 27, 1983 Perfil de Velocidade de Ventos na BÍixa Atmosfera

Celso Arami Marques da Silva - May 19, 1983 Estudo Difratométrico de Intermetálicos Pseudo-Bínários do Tipo

Zr(Fei-xSÍx)2

Marcus Vinícius Fontana Copetti - Oct. 17, 1983 Indicadores de Idade de Regiões HII

Rita Maria Cunha de Almeida - Oct. 24, 1983 0 Princípio de Pauli para Partículas Estendidas na Matéria Nuclear

Trieste dos Santos Freire Ricci - Oct. 26, 1983 0 Princípio de Pauli para Partículas Estendidas num Potencial Cen- tral

Claus Martin Hasenack - Dec. 14, 1983 Recozímento Isotérmico Rápido de Silício Implantado com ArcSnio -156-

Manuel Rubem Olcay Gonzalez - Dec. 20, 1983 Sintonização de urn Laser de Corante Pulsado para Espectroscopia de Alta Resolução

Andrea Latgè Alves de Souza - Jan. 31, 1984 Estudo Teórico de Impurezas Intersticiais de Hidrogênio em Metais ffc na Aproximação Cluster-Rede de Bethe

Gervásio Annes Degrazia - March 27, 1984 Dispersão Lateral de Poluentes na Baixa Atmosfera: Análise dos Ex_ perimentos de Hanford 67

Gilberto Luiz Ferreira Fraga - March 28, 1984 Estudo da Resistividade Elétrica de Ligas de Heusler do Tipo Ni-MnSn. In 2 1-x x

Maria de Fátima Saraiva Schrüder - Aug. 29, 1984 Fotometria Fotográfica Superficial das Galáxias NGC2855 e NGC6771

Sergio Mascarello Bisch - Sept. 28, 1984 Estudo sobre a Existincia de Componentes Periódicos da Variabili- dade em UBV de Núcleos de Galáxias Seyfert

Mareia Cristina Bernardes Barbosa - Oct. 2, 1984 Renormalização e Propriedades Críticas do Modelo de Potts Contí- nuo com Quebra Externa de Simetria

Osvaldo Luiz Leal de Moraes - Nov. 29, 1984 Perfil Vertical da Concentração de Poluentes na Atmosfera

Shirley Takeco Gobara - Dec. 6, 1984 Mapas Conceituais como Instrumentos Didáticos no Ensino da Física

Ph.D. THESES - 1983 and 1984

Luiz Fernando Ziebel - April 8, 1983 Amplificação de Radiação de Cíclotron Eletrônica em Plasmas Term£ nucleares -157-

Horacio Alberto Dottori - Aug. 26, 1983 Espectros de Absorção, Contínuo óptico e Avermelhamento em Núcleos Normais e Ativos de Galáxias Espirais

João Batista Marimon da Cunha - Dec. 9, 1983 Estudo da Anisotropia Magnética nos Compostos Intermetalicos

ErFe3Hx e (Er^Gd^F.j

Carlos Alberto dos Santos - Oct. 5, 1984 Composição Superficial e Propriedades Mecânicas e Tribológicas de Aços Carbono Implantados com Nitrogênio -158-

STÂFF MEMBERS OF THE DEPARTMENT OF PHYSICS

Amaral, L. (Ph.D.) On leave at Orsay, France since 8/30/83 Aveline, A. (M.Sc.) On leave since 3/01/84 Aveline, I.M.S. (Ph.D.) Axt, R. (M.Sc.) Baibich, M.N. (Ph.D.) Baumvol, I.J.R. (Ph.D.) Behar, M. (Ph.D.) Bonilla, I.R. (Ph.D.) Brandão, D.E. (Ph.D.) Bruschi, E. (M.Sc.) Buchweitz, B. (Ph.D.) Carvalho, R.M.V. (M.Sc.) Corrêa, M.H.P.F.V. (M.Sc, Costa, M.E.V. (M.Sc.) Costa Jr., M.I. (Ph.D.) Cunha, J.B.M. (Ph.D.) Cunha, S.L.S. (M.Sc.) On leave at Max-Planck Institut fUr Quantum Optik, Munich, West Germany Dillenburg, D. (Ph.D.) Dionision, P.H. (M.Sc.) Epstein, M. (Ph.D.) Francke, R.E. (Ph.D.) Fries, S.G. (M.Sc.) Girotti, H.O. (Ph.D.) Goedert, J. (Ph.D.) On leave at Los Alamos National Laboratory, Los Alamos, New Mexico, USA, from 3/02/83 to 2/01/85 Guimarães, L.B. Guimarães, V.H. Gusmão, M.L.V. (M.Sc.) Gusmão, M.A.C. (Ph.D.) Herscovitz, V.E. (Ph.D.) Igle8Ías, J.R. (Ph.D.) Jacob* G. (Ph.D.) Jornada, E.H. (Ph.D.) On leave at Maryland University, USA, from 4/06/83 to 8/01/84 Jornada, J.A.H. (Ph.D.) On leave at Natioual Bureau of Standards, Washington DC, USA, from 4/06/83 to 8/01/84 -159-

Kunrath, J.I. (Ph.D.) Kunzler, J.V. (Ph.D.) Laier, W. Levandowski, C.E. (Ph.D.) Liberman, B. (Ph.D.) Livi, F>P. (Ph.D.) Livi, R.P. (Ph.D.) On Leave at W.K. Kellog Radiation Laboratory, California, USA, from 3/21/83 to 2/28/85 Maciel, A. (Ph.D.) Maris, Th.A.J. (Ph.D.) Medeiros, J.T.N. (Ph.D.) Medero, I.M. (M.Sc.) Medero, J.L. (M.Sc.) Moreira, M.A. (Ph.D.) Mors, P.M. (M.Sc.) Müller, C.S. (Ph.D.) Mundt, W.A. (M.Sc.) Petry, P.P. (Ph.D.) Pureur Neto, P. (Ph.D.) On leave at Laboratoire de Physique des Solides, Universitê Paris-Sud, Orsay, France Schaf, J. (Ph.D.) Scherer, C. (Ph.D.) Schmidt, J.E. (Ph.D.) Schneider, C. (Ph.D.) Schneider, R.S. (Ph.D.) Schreiner, R.L. Schreiner, W.H. (Ph.D.) Silva, M.T.X. (M.Sc.) Silveira, F.L. (M.Sc.) Simões, T.J.M. (M.Sc.) Souza, J.P. (Ph.D.) Stezfani, M.H. (M.Sc.) Teixeira, R.R. (Ph.D.) Teixeira, S.R. (M.Sc.) Teodoro, M.R. (Ph.D.) Theumann, A. (Ph.D.) Theumann, W. (Ph.D.) Vasconcellos, C.A.Z. (M.Sc.) -160-

Vasquez, A. (Ph.D.) Veit, E.A. (Ph.D.) On leave at University of British Columbia, Vancouver, Canada, from 9/06/82 to 9/05/84 Viccaro, M.H.A. (Ph.D.) Viccaro, P.J. (Ph.D.) Wackerritt, H.H.K.E. Zawislak, B.M.M. (M.Sc.) Zawislak, F.C. (Ph.D.) Zawislak, L.I. (M.Sc.) Ziebel, L.F. (Ph.D.) On leave at Centre d'Etudes Nucléaires, Gre- noble, France since 8/01/84

STAFF MEMBERS OF THE DEPARTMENT OF ASTRONOMY

Bergmann, T.S. (M.Sc.) Dottori, H.A. (Ph.D.) Ducati, J.R. (Ph.D.) Livi, S.H.B. (M.Sc.) On leave at Department of Astronomy, Pasadena, California, from 3/21/83 to 2/28/85 Oliveira F9, K.S. (Ph.D.) On leave at University of Texas, Austin, USA Pastoriza, M.G. (Ph.D.) Vieira, E.R. (Ph.D.)

ENGINEERING STAFF OF THE INSTITUTE OF PHYSICS

Boos Jr., A. Fachin Jr., M. Fin, M. Wyrzykowski, M.P, Zimmermann, S. On leave at Fermi National Accelerator Lab., Illinois, USA Bulla, A.A. -161-

GRADUATE STUDENTS OF THE INSTITUTE OF PHYSICS

Ph.D. students

Almeida, R.M.C. Aveline, A. Barbosa, M.C.B. Bergmann, T.S. Brunnet, L.G. Caldela F9, R.A. Copeti, M.V.F. Corria, M.H.P.F.V. Correia, F.H.G Costa, M.E.V. Costa, J.A.T.B. Cruz F9, S.P. Cunha, J.B.M. Dionisio, P.H. Dottori, H.A. Fichtner, P.P.P. Fraga, G.L. Fries, S.G. Garcia, V.H. Guimarães, R.B. Gusmão, M.L.V. Hasenack, CM Krein, G.I. Lisboa, J.A. Medero, I.M. Medero, J.L. Milman, F.S. Mors, P. Mundt, W.A. Ogiba, F. Oliveira, L.S. Olivieri, C.A. Paesano Jr., A. Palandi, J. -162-

Pureur Neto, P. Ricci, T.S.F. RBpke, U.O. SchrBder, M.F.S. Silva, M.T.X. Simões, À.S.R. Simões, T.J.M. Steffani, M.H. Teixeira, S.R. Vasconcellos, C.A.Z, Zawislak, L.I.

M.Sc. students

Almeida, R.M. Barbosa, M.C.B. Bellé, M.J. Bisch, S.M. Bonatto, C.J. Braum, T. Brusch, L.R.F. Carrasco, H.J.D. Consiglio, R. Copetti, M.V.F. Cotta, R.D.D. Costamilan, G.B. Dagnino, R.P. DeGrazia, G.A. Dellepiane, M.E.D. Erichsen Jr., R. Escobar, W.A. Ferlin, E.L. Fraga, G.L.F. Gobara, S.T. Gonzalet, M.R.O. Benz, C.F. Hickaann, J.S. -1 63-

Louzada, J.A.C. Moraes, O.L.L. Oliveira, C.R.M. Pasa, A.A. Rad, M.H.G. Ramos, S.M.M. Ricci, T.S.F. Rizzato, F.B. Rosa, P.R.S. Ruas, CA.A. Santos, A.C.K. Scherer, E.M. Schmidt, A.A. Schrüder, M.F.S. Silva, L.E.F. Souza, A.L.A. Sommer, R.L. Vasconcellos, M.A.Z. Vaz, R.L.