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UBC Theses and Dissertations

On the theory of radiative electron capture Paquette, Guy

Abstract

The continuous spectrum of gamma radiation which accompanies the capture of orbital electrons has been recently calculated independently by Glauber and Martin (1954), and by Hess (1955). Both calculations take into account the influence of the nuclear charge on the wave functions but otherwise involve different methods and approximations, the conclusions being also quite different: the intensity of the gamma radiation is an order of magnitude lower according to Hess than according to Glauber and Martin. The purpose of the calculations presented in this thesis has been to settle this disagreement and to explain its origin. To this effect the high energy part of the gamma spectrum, which is almost entirely determined by the contributions of the capture of the 1s and 2s electrons, has been computed for the case of A³⁷ for which experimental data are available. In view of the low nuclear charge of A³⁷ (z = 18), the non-relativistic Coulomb wave functions could be used, and, apart from neglecting screening effects, the calculations are exact although partly numerical. In particular, the retardation effects which were neglected by Glauber and Martin have rigorously been taken into account. The conclusions are: first, approximations used by Hess were partly inconsistent, although the method was in principle correct; second, taking into account retardation effects results in a gamma spectrum whose intensity amounts to 0.81 of the intensity obtained by Glauber and Martin at 135 Kev, and to 0.24 at 675 KeV (the gamma spectrum limit being 816 KeV). The gamma spectrum of A³⁷ determined by Lindqvist and Wu (1955) seems to agree quite well with Glauber and Martin's result. However, Lindqvist and Wu measured only relative intensities and had to apply many instrumental corrections so that it is not yet clear whether the measured spectrum would not agree as well with the spectrum computed in this thesis.

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