Nuclear Structure Effects in Internal Conversion Coefficients by Configuration Mixing

The nuclear matrix elements which are needed to determine the internal conversion coefficients when a finite nucleus is employed are derived for nuclei for which the shell model wave functions are a good zero-order approximation for low-energy processes. Using configuration mixing, general expressions are derived for these matrix elements. It is shown that the nuclear structure alteration can be ten to twenty percent or more for $l$-forbidden transitions. Numerical results are given for the $M1\mathrm{}$ and $E2\mathrm{}$ 279-kev transitions in ${\mathrm{Tl}}^{203}$.