A direct measurement of the $\frac{M}{L}$- and $\frac{L}{K}$-orbital electron-capture ratios in the decay of ${\mathrm{Cd}}^{109}$ was carried out by using a gaseous radioactive source of ${\mathrm{Cd}}^{109}$ ${\left(\mathrm{C}{\mathrm{H}}_3\right)}_2$ in a multiwire proportional counter with internal anticoincidence. The experiments yielded the following values of the orbital electron-capture probability ratios: $\frac{P_M}{P_L}=0.232\mathrm{}\pm 0.020$, $\frac{P_{L+M+\cdots }}{P_K}=0.332\mathrm{}\pm 0.015$, and $\frac{P_L}{P_K}=0.237\mathrm{}\pm 0.015$. From the $\frac{P_L}{P_K}$ value, the transition energy for capture to the 88-keV ($\frac{7}{2}+$) state in ${\mathrm{Ag}}^{109}$ was found to be $Q_{\mathrm{EC}}={{80}_{-3\mathrm{}}}^{+7\mathrm{}}$ keV by application of the theory. The experimental $\frac{M}{L}$-capture ratio is in excellent agreement with the exchange-corrected theoretical result extrapolated from Bahcall (0.230) and with the theoretical results of Robinson.

• Received 1 March 1965

DOI:https://doi.org/10.1103/PhysRev.139.B282