Proportional counter studies of orbital electron capture ratios

Dougan, Peter W (1961) Proportional counter studies of orbital electron capture ratios. PhD thesis, University of Glasgow.

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The first chapter of the thesis summarizes briefly the theoretical treatment of orbital electron capture. Particular attention is given to the theoretically-obtained wave function ratios which are available for comparison with experimental values. It is pointed out that, when calculating values of atomic electron wave functions, it is customary not to consider the correlations which must exist among the atomic electrons, and that when such correlations are considered, the theoretical values for L/K-ratios are increased over those obtained from the use of hydrogen-like functions. A comparison of theoretical and experimental values of L/K-ratios is made and it is shown that further experimental work is required in all ranges of atomic number. In particular, the range of atomic number between 15 and 40 is shown to be suitable for investigation. The second chapter describes the characteristics required in the detection system and outlines the wall-less counter technique used by the author. The experimental work is described in the next four chapters. Measurements of L/K-ratios in the isotopes germanium-71, krypton-79, chlorine-36 and argon-37 are described, together with Incidental points of counter technique which were clarified in the course of the measurements. The values of 0.116 +/- 0.005, 0.108 +/- 0.005, 0.112 +/- 0.008 and 0.102 +/- 0.004, obtained for the L/K-ratios in these isotopes, are greater than the respective theoretical values of 0.106, 0.101, 0.080 and 0.082 calculated from the ratios of wave functions prepared by Brysk and Rose. The difference between theory and experiment is most marked for isotopes of small atomic number. This is in accord with the predictions of Odiot and Daudel, who evaluated the effect of the electron correlations in light isotopes. Their value of 0.100 for the L/K-ratio in argon-37 is in good agreement with that obtained in the present work. Capture from the M-shell was detected in germanium-71 and krypton-79, the first direct observation of capture from this shell in isotopes with mass number less than 200. The values of the ratio of M-capture to L-capture in both isotopes was found to be 0.16 +/- 0.08, in reasonable agreement with the ratios of electron density given by Hartree wave functions. Indications that M-capture occurred also in chlorine-36 and argon-37 were observed, but the evidence cannot be considered to be conclusive. The final chapter of the thesis summarizes the above results and, after comparison of the available theoretical and experimental values of L/K-ratios, concludes that further theoretical work to evaluate the magnitude of the electron correlations as a function of atomic number is necessary. There are four appendices. The first contains analytical forms of the wave functions of an electron in the Coulomb field of a point charge, while the second gives some details about the counters used in the measurements. In the third, are some brief remarks about the new electronic units added in the course of the measurements. The fourth discusses measurements undertaken to establish the presence of a positron branch in the decay of chlorine-36. It is shown that the observations are consistent with the existence of a weak branching, of intensity K/beta+ = 1500 +/- 300 500 relative the X-capture component of the source.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: P I Dee
Keywords: Atomic physics
Date of Award: 1961
Depositing User: Enlighten Team
Unique ID: glathesis:1961-73496
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56

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