Internal Conversion Coefficients ofM1Gamma Rays ofAu199andAu195

Abstract

An attempt has been made to measure the internal conversion coefficients of the $M1+E2\mathrm{}$ radiations of ${\mathrm{Au}}^{199}$ and ${\mathrm{Au}}^{195}$ with sufficient accuracy to check the effect of the finite nuclear size on internal conversion in this region of $Z$. In the case of ${\mathrm{Au}}^{199}$ a direct comparison of the 158-kev pure $E2\mathrm{}$ transition with the 208-kev $M1+E2\mathrm{}$ radiation was possible. Comparison of the gamma-ray intensities determined from scintillation spectrometry with conversion line intensities measured in a small shaped-field spectrometer yielded $K$, $L$, $M$, total shell coefficients. Comparison of these gamma-ray intensities with conversion line intensities photographically recorded in a higher resolution permanent-field spectrometer led to $L$-subshell coefficients. The results for the 208-kev transition are: $a_K=0.71\mathrm{}\pm 0.05$, $a_L=0.144\mathrm{}\pm 0.01$, $a_{L\mathrm{I}}=0.114\mathrm{}\pm 0.007$, $a_{L\mathrm{II}}=0.0227\mathrm{}\pm 0.0007$, $a_{L\mathrm{III}}=0.0065\mathrm{}\pm 0.0005$, $a_M=0.042\mathrm{}\pm 0.04$, and $a_{N+O}=0.0083\mathrm{}\pm 0.001$. The empirical multiplicative factors $f$ by which point-nucleus theoretical values are to be reduced, presumably due to the finite nuclear effect, and the $E2\mathrm{}$ mixing ratio $r$ have been determined: $f_K=0.762\mathrm{}\pm 0.08$, $f_{L\mathrm{I}}=0.78\mathrm{}\pm 0.13$, $f_{L\mathrm{II}}=1.00\mathrm{}\pm 0.06$, $f_{L\mathrm{III}}=1.0\mathrm{}$, and $r=0.11\mathrm{}\pm 0.03$. These results, insofar as they may be compared, are not inconsistent with Sliv's predictions ($f_K=0.8\mathrm{}$). An experimental value of 0.60 was found for the screening correction to Rose's $M$-shell coefficients for this $Z$ and energy region.