Conversion Coefficients of the Fe57 14.4-keV Transition, the K-Capture Fraction in Co57 e− Capture, and the K-Fluorescence Yield of Fe

Abstract

By x-x and $\mathrm{x}-\gamma$ coincidence-counting a ${\mathrm{Co}}^{57}$ → ${\mathrm{Fe}}^{57}$ source with gas proportional counters, we obtain the values ${\alpha }_K{\omega }_K=2.484\mathrm{} (\pm 1.8\%)$, $f{\omega }_K=0.3044\mathrm{} (\pm 1.4\%)$, and $\frac{S}{({\alpha }_T+1)}=0.09482\mathrm{} (\pm 2.3\%)$, where ${\alpha }_K$ and ${\alpha }_T$ are the $K$ and total conversion coefficients of the ${\mathrm{Fe}}^{57}$ 14.4-keV $\gamma$ ray, ${\omega }_K$ is the $K$-fluorescence yield of Fe, $S$ is the probability that the ${\mathrm{Fe}}^{57}$ 136.4-keV level decays to the 14.4-keV level, and $f$ is the fraction of $K$ captures in ${\mathrm{Co}}^{57}$ $e^{-}$ capture. These numbers are consistent within narrow limits with others' reported precise measurements of $S$, $f$, and the ratio $\frac{{\alpha }_K}{{\alpha }_T}$. With the use of the values $S=0.87\mathrm{} (\pm 1.7\%)$ and $\frac{{\alpha }_K}{{\alpha }_T}=0.89\mathrm{} (\pm 0.15\%)$ from electron-spectrometer measurements reported by others, we obtain ${\alpha }_T=8.17\mathrm{} (\pm 3.1\%)$; ${\alpha }_K=7.27\mathrm{} (\pm 3.1\%)$; $f=0.891\mathrm{} (\pm 3.85\%)$; ${\omega }_K=0.342\mathrm{} (\pm 3.6\%)$. Our value of ${\alpha }_T$ is 9% lower than that reported for some half-dozen measurements by $\gamma -\gamma$ coincidence counting and by Mössbauer methods, all of which cluster...