Israel Atomic Energy Commission • \ IA-1404
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IA-1404 Israel Atomic Energy Commission • \ IA-1404 /• Israel Atomic Energy Commission AVAILABILITY Israel Atomic Energy Commission reports and bibliographies may be obtained from Technical Information Department Israel Atomic Energy Commission P.O.Box 7061, 61 070 Tel-Aviv, ISRAEL CONTENTS I MATHEMATICS,THEORETICAL PHYSICS AND THEORETICAL CHEMISTRY 1 II REACTOR PHYSICS AND REACTOR SAFETY 22 ^•••••HIBaBHHiHBHBHHHIMBBHHlBHiHBBraHl III PLASMA PHYSICS AND PLASMA CHEMISTRY 51 IV LASERS AND SPECTROSCOPY 63 V SOLID STATE PHYSICS AND CHEMISTRY 77 VI MATERIALS SCIENCE 97 VII NUCLEAR PHYSICS AND NUCLEAR CHEMISTRY 127 VIII GENERAL, PHYSICAL AND RADIATION CHEMISTRY 139 IX RADIOISOTOPES, LABELED COMPOUNDS AND BIOSCIENCES 159 X- RADIATION SAFETY AND ENVIRONMENTAL STUDIES 199 XI INSTRUMENTATION AND TECHNIQUES 217 XII DOCUMENTATION 235 XIJJL AUTHOR INDEX 273 Some of the studies connected with nuclear pow*>r plants are performed in cooperation and coordination with the Ministry of Energy and Infra structure which has ministerial responsibility in this field. IA-1404 Israel Atomic Energy Commission RESEARCH LABORATORIES ANNUAL REPORT, 1983 July 1984 280 p. This report presents brief summaries of the research carried out at the Israel A.E.C. laborato ries during 1983. FOREWORD This annual report of the Israel Atomic Energy Commission presents an overview of the research activities in 1983. Its content covers, once again, a broad spectrum of theoretical and experimental programs in basic and applied physics, chemistry, materials and life sciences and environmental studies. The list of topics shows no major departures from previous years and represents a continuing and developing process of in-depth studies in well established directions. The preparatory work related to the construction of nuclear power plants in Israel was continued in coordination with the Ministry of Energy and Infrastructure, and its recently appointed Nuclear Power Plant Program Steering Committee. Most of the effort was devoted to safety and security problems, site evaluation and reactor studies. A long term program for the enhancement of local technological and engineering capabilities in the field of nuclear power was submitted to the steering committee. Another major field of endeavor concerns medical, industrial and agricultural applications of nuclear and radiation-based techniques and technologies. Following are some examples of the extent and success of this program. - The steadily growing demand of the Israeli nuclear medicine community for radiopharmaceuticals is being met almost entirely by products developed and manufactured under the auspices of the Israel Atomic Energy Commission. - A large number of labeled compounds for medical and biological research have been synthesized. - Radioactive tracers have been applied to a wide variety of hydro- logical, industrial and environmental problems. - Advanced radiographic and other NDT techniques are finding increasing uses in industry, and have been successfully applied to the study of unique archeological artifacts. - Radiation sterilization of medical disposables is carried out on a commercial basis. • - A very recent development is the establishment (in cooperation with enterprises abroad and a leading animal feed producer) of a large scale demonstration plant for the radiatior. treatment of poultry feed, to obtain pathogen-free poultry products. - Processes for the production of improved plastic materials by radiation-induced crosslinking or grafting techniques have been developed. Some of them have already been licensed to industries for full scale implementation. The IAEC considers these non-power applications of nuclear energy as an important and highly beneficial aspect of its activity, and hopes to continue and expand its work in these areas. Tel Aviv Viz.? Eilam July 1984 Director General IAEC :» -j^W t»W-& • **T M i*"*^ *W » .* fc> > i t« • -**J i . f '»\ * -'._ «nV 4 \A 3 3 5- ' ' - ' , • i * i ' "'"I i - 3 - APPROXIMATE GREEN FUNCTION FOR A SEMI-INFINITE SOLID WITH VARYING PROPERTIES^ R. Englman An expression was derived for the spatially dependent Green function or response function in a solid occupying a half-space and having generally varying properties. The expression is valid in the same range as the WKB approximation, namely for slowly varying prop erties. Some generalization is indicated and the time-dependent Green function or the resolvent is obtained as a Fourier transform. REFERENCE: 1. Englman, R., J. Phys. A 16, 2939 (1983) NONRADIATIVE TRANSITIONS BY PATH INTEGRAL WITH THE USE OF SEMICLASSICAL APPROXIMATIONS^ R. Englman, A. Agresti ' , D. Mugnai and A. Ranfagni Tunneling transition rates were evaluated for a two-mode system in the semiclassical (WKB) approximation with inclusion of contribu tions of neighboring paths to the classical one, connecting two given points, or by considering a distribution of classical paths. Neigh boring paths increase the transmission coefficient in the cases of a single-saddle-point barrier by about 6%, while in the case of two or three saddle points this rise can reach 100%. Thus the considera tion of several classical paths is important if there are several least-action paths, e.g., for symmetry reasons. This formalism was then applied to nonradiative transitions occurring in color centers. In particular, we reconsidered temperature dependence of the A and + A^ emissions in Tl centers, which is a typical case of a three- saddle-point barrier. REFERENCE: 1. Englman, R., Agresti, A., Mugnai, D. and Ranfagni, A., Phys. Rev. B 28., 4307 (1983) * Istituto di Ricerca sulle Onde Elettrotnagnetiche del Consiglio Nazionale delle Ricerche, Firenze, Italy && * Dniversita degli Studi di Firenze, Firenze, Italy - 4 - INCLUSION OF NEIGHBORING PATHS IN THE EVALUATION OF NON-RADIATIVE PROCESSES BY SEMI-CLASSICAL APPROXIMATIONS^ R. Englman, D. Mugnai ' and A. Ranfagni In the normal application of semi-classical procedures one calculates configurational changes of impurity centres in solids in terms of transition along a single pathway (the classical path) only. In our extension of this procedure we included neighboring-path contribu tions to the classical one. In doing so, we encountered a problem of normalization of the (WKB-) wave function. Having proposed a suitable normalization criterion, we were able to obtain simple expressions for the tunneling transition in the semi-classical approximation. One differentiates between cases of one, two and three saddle-points along the trajectories. REFERENCE: 1. Englman, R., Mugnai, D. and Ranfagni, A., Phys. Lett. 94A, 12 (1983) TUNNELING CONTRIBUTION IN NON-RADIATIVE PROCESSES^ R. Englman, A. Ranfagni , D. Mugnai and A. Agresti A semiclassical formalism, previously introduced to treat non- radiative processes in multidimensional spaces, was extended to compute total non-radiative transition rates. A simple approximate analysis results in simple formulae which discriminate between quantum- tunneling contributions and classical ones. Applications to diffusion processes of vacancies in solids were made and temperature regions were distinguished where tunneling is comparable to or exceeds barrier jumping. For the (111) jump of the vacancy in lithium metal, the motions of six neighboring ions were taken into account to simulate vacancy jumps. Below 25K the tunneling contribution dominates and remains comparable to the classical process up to about 335K (the Debye temperature of the metal). REFERENCE: 1. Englman, R., Ranfagni, A., Mugnai, D. and Agresti, A., Solid State Commun. ,4_7, 723 (1983) __ Scuola di Perfezionamento in Fisica dell 'Universita di Firenze, Aj).Firenze, Italy Istituto di Ricerca Sulle Onde Elettromagnetiche del CNR, Firenze, Italy - 5 - COMPETITION BETWEEN RADIATIVE AND NON-RADIATIVE DECAYS LEADS TO A DIP IN THE EMISSION LINESHAPE^ * * R. Englman, A. Ranfagni and D. Mugnai In this work an anomalous lineshape in the emission spectra of defects was theoretically predicted. The anomalous shape may have been seen by us previously in the low temperature magnetic-circular polarization spectrum of K1:T1 . It almost certainly appears in the W and M„ bands due to molecular excitons in rare gas crystals. We computed the emission spectra of relaxing excited-state systems in solids as a function of the rates of radiative decay from excited- to-ground state and non-radiative decay within the excited state. When these are comparable, a pronounced dip is obtained in the central region of the spectrum, which then may have the appearance of two,distinct, independent emission bands. REFERENCE: 1. Englman, R., Ranfagni, A- and Mugnai, D., Radiat. Eff. _7_3» 291 (1983) SURFACE MODES AND OPTICAL ABSORPTION OF A SMALL SPHERE ABOVE A SUBSTRATE R. Ruppin The electrostatic surface modes of a sphere above a substrate were derived exactly. The absorption spectrum of the sphere was calculated and compared with that of an isolated sphere. The inter action with the substrate causes the main absorption peak to shift to the low frequency side, and also gives rise to additional absorp tion peaks. The deficiencies of the dipole approximation, which is often used, were considered. REFERENCE: 1. Ruppin, R., Surface Sci. 127, 108 (1983) Istituto di Ricerca sulle Onde Elettromagnetiche del CNR, Firenze, Italy - 6 - FORMATION OF GAS BUBBLES IN GAS SUPERSATURATED WATER * Y. Finkelstein and A. Tamir The phenomenon of bubble formation in gas supersaturated water solutions is a transport process, which results in the separation of phases. In