Determination of the absolute K through O conversion coefficients of the 80-keV M4 transition in 193Irm.

Abstract

We produced carrier-free, nearly isotopically pure $^{193}\mathrm{Ir}^{\mathrm{m}}$ from thermal-neutron irradiation of $^{192}\mathrm{Os}$. From studies of the conversion-electron spectrum, the photon spectrum, and the absolute counting rates, we determined the absolute K, L1, L2, L3, M1, M3, M5, N, and O+P conversion coefficients for the first time. With possibly one exception, these values agree closely with theoretical calculations. The value for the energy of the unconverted gamma ray was found to be 80.22\ifmmode\pm\else\textpm\fi{}0.02 keV. The half-life for $^{193}\mathrm{Ir}^{\mathrm{m}}$ determined by absolute electron counting in a proportional counter of 100% counting efficiency (4\ensuremath{\pi}\ensuremath{\beta}) was found to be 10.53\ifmmode\pm\else\textpm\fi{}0.04 d. We have determined the ${L}_{1}$ subshell fluorescence yield, ${\ensuremath{\omega}}_{1}$, to be 0.120\ifmmode\pm\else\textpm\fi{}0.003 for iridium. Based upon our measurements of initial and final L subshell vacancies together with a best-fit literature value for ${\ensuremath{\omega}}_{2}$, we have found a plausible value for the Coster-Kronig coefficient ${f}_{12}$ to be 0.091\ifmmode\pm\else\textpm\fi{}0.011.