Empirical Screening Correction forM-Subshell Internal Conversion Coefficients

Abstract

The only theoretical values which are available for coefficients of internal conversion in the $M$ shell have been calculated without the inclusion of screening, and they are in disagreement with experimental values by factors as large as 3. From the comparison of these theoretical values with new accurate measurements on the $M$-subshell electron lines of the $M4\mathrm{}$ transitions occuring in the decay of ${\mathrm{Te}}^{121m}$ and of ${\mathrm{Te}}^{123m}$, it was possible to effect a tentative semiempirical screening correction. Essentially, this is the replacement of the nuclear charge $Z$ for the evaluation of the coefficient by $Z_{\mathrm{eff}M}=Z-{\sigma }_i$, where ${\sigma }_i=7.0, 7.9, \mathrm{and} 10.0$ for $M_{\mathrm{I}}\mathrm{}\left(3s\right)\mathrm{}$, $M_{\mathrm{I}\mathrm{I},\mathrm{I}\mathrm{I}\mathrm{I}}\mathrm{}\left(3p\right)\mathrm{}$, and $M_{\mathrm{I}\mathrm{V},\mathrm{V}}\mathrm{}\left(3d\right)\mathrm{}$ electrons, respectively. This correction to the theoretical values is found to produce agreement with other experimental $M$ conversion results, both measured in this work and taken from the literature, over a wide range of multipolarities and of $Z$ and energy values. The nonspecific characteristic of the correction is interpreted to mean that the screening is chiefly an effect on the electron wave functions of the initial bound states of the atom.