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Measurements of Some Internal Conversion Coefficients Using Scintillation Counter, Coincidence Techniques Ronald S Ames Laboratory Technical Reports Ames Laboratory 2-1964 Measurements of some internal conversion coefficients using scintillation counter, coincidence techniques Ronald S. Dingus Iowa State University W. L. Talbert Jr. Iowa State University E. N. Hatch Iowa State University Follow this and additional works at: http://lib.dr.iastate.edu/ameslab_isreports Part of the Physics Commons Recommended Citation Dingus, Ronald S.; Talbert, W. L. Jr.; and Hatch, E. N., "Measurements of some internal conversion coefficients using scintillation counter, coincidence techniques" (1964). Ames Laboratory Technical Reports. 85. http://lib.dr.iastate.edu/ameslab_isreports/85 This Report is brought to you for free and open access by the Ames Laboratory at Iowa State University Digital Repository. It has been accepted for inclusion in Ames Laboratory Technical Reports by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Measurements of some internal conversion coefficients using scintillation counter, coincidence techniques Abstract Internal conversion coefficients were measured by observing with a well-type Nal(Tl) crystal the photon spectra emitted during the de-excitation from the first excited state to the ground state of Gdl54,D)y 160, Ybl70, Ybl71 and Prl41 following the respective beta decays of Eul54, Tbl60, Tm170, Tml71 and Cel41. The results were obtained by analysis of either the singles spectra, or spectra obtained by coincidence-sum techniques, or both. For the coincidence work gating was done either with high energy gamma rays or with beta particles. The spectra from the Yb isotopes were analyzed on a computer using a least-squares curve- fitting program. The hotp on detection efficiencies, necessary for the measurements, were calculated with a computer by performing numerical integrations. The following K-shell internal conversion coefficients were measured directly for first excited state to ground state transitions: 0.632 ± 0.016, for Gdl54; 1.48 ± 0.05, for Ybl70; 6.9:1: 1.0, for Ybl71 and 0. 375 ± 0. 009, for Prl41. The ott al internal conversion coefficients were measured for the first excited state to ground state transitions in Gdl54 and nyl60 and found to be 1. 20 ± 0. 02 and 4. 52± 0. 11, which yield respective K-shell internal conversion coefficients of 0. 637 ± 0. 016 and 1. 54± 0. 06 when multiplied by K to total ratios. The er sults for these 2+->0+ transitions in Gdl54 and Dyl60 and for this -t -forbidden Ml transition in Prl41 are in good agreement with theory. The ar tio of the experimental result to the theoretical value is 1. 09 ± 0. 06 for this 2+-0+ transition in Ybl 70. The er sult for this Ml + E2 transition in Ybl71 implies a mixing ratio of E2/Ml = 0. 45 :±. 0. 09, assuming the theoretical internal conversion coefficients are correct. Disciplines Physics This report is available at Iowa State University Digital Repository: http://lib.dr.iastate.edu/ameslab_isreports/85 PIIYSICA • SCTENCF.S READ G IOWA STATE UNIVERSITY MEASUREMENTS OF SOME INTERNAL CONVERSION COEFFICIENTS USING SCINTILLATION COUNTER, COINCIDENCE TECHNIQUES by R onald S. Dingus, W. L. Talbert, Jr. and E. N. Hatch RESEARCH AND . DEVELOPMENT ( REPORT U.S.A.E.C. IS-1032 Physics (UC-34 TID 4500, January 1. 1965 UNITED STATES ATOMIC ENERGY COMMISSION Research and Development Report MEASUREMENTS OF SOME INTERNAL CONVERSION COEFFICIENTS USIN SCINTILLATION COUNTER. COINCIDENCE TECHNIQUES by Ronald S. Dingus. W. L. Talbert. Jr. and E. N. Hatch February. 1965 Ames Laboratory at Iowa State University of Science and Technology F. H. Spedding. Director Contract W-7405 eng-82 ii IS-1032 This report is distributed according to the category Physics (UC-34) as listed in TID-4500, January 1, 1965. r-------- LEGAL NOTICE_;,_______ __, This report was prepared as an account of Government sponsored work. Neither the United States, nor the Commission, nor any person acting on behalf of the Commission: A. Makes any warranty or representation, expressed or implied, with respect to the accuracy, completeness, or usefulness of the information contained in this report, or that the use of any information, apparatus , method, or process disclosed in this report may not infringe privately owned rights; or B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of any information, apparatus, method, or process disclosed in this report. As used in the above, "person acting on behalf of the Commission" includes any employee or c ontractor of the Commission, or employee of such contractor, to the e x t e nt that such employee or contractor of the Commission, or employee of such contractor prepares, disseminates, or provides access to, any information pursuant to his employment or contract with the Commission, or his employment with such contractor. Printed in USA. Price $4.00 Available from the Clearinghouse for Federal Scientific and Technical Information, National Bureau of Standards, U. S. Department of Commerce, Springfield, Virginia iii IS-1032 TABLE OF CONTENTS Page ABSTRACT v I. INTRODUCTION 1 A. The Internal Conversion Process 1 B. Remarks on the Theory 6 C. Methods of Measurement 11 D. Agreement of Experiment and Theory 14 II. MEASUREMSNT 3Y PHOTON SPECTRt M ANALYSIS 19 A. Basic Photon Method 19 B. Coincidence-Sum Method 24 1. No internal summing ?.9 a . Uniquely gate with ry, ~~ or v 29 b. Gating with X-rays 35 2. With internal summing JB a . Gate on v followi!'lg K capture JS b. Two coincident transitions gated by ry, R, or v 40 J. Triple coincidence method 42 4. Advantages and disadvantages 43 III. EXPERIMENTAL INVESTIGATIO N 45 A. Measurement of the Total and K-Shell Internal Conversion Coefficients for the Ground State 154 160 Rotational E2 Tr ansitions in Gd and Dy 45 1. General procedure 45 iv IS-1032 Page 2. Gd154 spectrum analysis so J. Dy160 spectrum analysis 56 B. Mea surement of the K-Shell Internal Conversion Coefficients for the Low Energy, Ground State Transitions in Yb170, Yb171 and Pr141 1. Genera l procedure 2. Ybl71 spectrum analysis 69 J. Yb170 spectrum analysis 73 4. Pr141 spectrum analysis 81 IV. SOl'JCLUSION 85 A. E2 Tr ans itions 85 B. ~ 1 + E2 Transitions 92 V. APPENDIX A: GAM ~ A - BAY EFFICIENCIES FCR ~ ELL- 'T'PE SC H·~TI LLATICF CPYSTALS 94 A. ~lethod B. Checks on the Calculations 99 c. Typical Results for Common Crystals 101 VI. APPeNDIX E: LEAS'r S~Ut\ "R.E.:S A EAL~SIS OF GA rt:fviA - RAY S~ECTP.A 106 A. Type of Approach Used 106 B. The ?esponse below the Photopeak 108 C. Versatile Function for Fitting Non­ Gaussian Peaks 113 VII: APPEND IX C: NOTE ON THE ENERGY CF THE Ag109 ISOMERIC TPANSITICN 116 VIII. BIBLIOGRAPHY 11 9 v. IS-1032 MEASUREMENTS OF SOME INTERNAL CONVERSION COEFFICIENTS USING SCINTILLATION COUNT-ER, COINCIDENCE TECHNIQUES Ronald S. Dingus, W. L. Talbert, Jr. and E. N. Hatch ABSTRACT Internal conversion coefficients were measured by observing with a well-type Nal(Tl) crystal the photon spectra emitted during the de­ excitation from the first excited state to the ground state of Gdl54, !)y 160, Ybl70, Ybl71 and Prl41 following the respective beta decays of Eul54, Tbl60, Tm170, Tml71 and Cel41. The results were obtained by analysis of either the singles spectra, or spectra obtained by coincidence-sum techniques, or both. For the coincidence work gating was done either with high energy gamma rays or with beta particles. The spectra from the Yb isotopes were analyzed on a computer using a least-squares curve­ fitting program. The photon detection efficiencies, necessary for the measurements, were calculated with a computer by performing numerical integrations. The following K-shell internal conversion coefficients were measured directly for first excited state to ground state transitions: 0.632 ± 0.016, for Gdl54; 1.48 ± 0.05, for Ybl70; 6.9:1: 1.0, for Ybl71 and 0. 375 ± 0. 009, for Prl41. The total internal conversion coefficients were measured for the first excited state to ground state transitions in Gdl54 and nyl60 and found to be 1. 20 ± 0. 02 and 4. 52± 0. 11, which yield respective K-shell internal conversion coefficients of 0. 637 ± 0. 016 and 1. 54± 0. 06 when multiplied by K to total ratios. The results for these z+-ot transitions in Gdl54 and nyl60 and for this -t -forbidden Ml transition in Prl41 are in good agreement with theory. The ratio of the experimental result to the theoretical value is 1. 09 ± 0. 06 for this z+-o+ transition in Ybl 70. The result for this Ml + E2 transition in Ybl71 implies a mixing ratio of E2/Ml = 0. 45 :±. 0. 09, assuming the theoretical internal conversion coefficients are correct. 1 I. I NTRODUCTION A. The Internal Conversion Process A nucleus in an excited state normally proceeds to a lower energy state by emitting a gamma ray whose energy is equal to the transition -energy or by an alternate process, internal conversion, in which the transition energy is g iven directly to one of the orbital electrons. This elec­ tron is then ejected from the atom with an energy equal to the transition energy minus the binding energy that the electron had in the atom . Internal conversion is not to be confused with a process, frequently designated as externa l conversion, in which an emitted gamma ray transfers its en­ e r gy to an orbital electron by photoelectric intera ction. There is a third mode of decay for excited nuclear sta tes which occurs when the nuclear transition energy is g rea ter than t wice the electron rest mass, 2mc2 (1.02 MeV).
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