Decay ofEu147to Levels inSm147

A recent investigation of the conversion-electron spectrum of ${}_{}{}^{147}{}_{}{}^{}\mathrm{Eu}$ has revealed numerous new transitions in ${}_{}{}^{147}{}_{}{}^{}\mathrm{Sm}$. The present study was undertaken to supplement these conversion-electron data with $\gamma$-ray information obtained with high-resolution Ge(Li) counters. Singles $\gamma$-ray spectra were obtained, and ${\beta }^{+}-\gamma \left(\mathrm{NaI}\right)$, $e-\gamma \left(\mathrm{NaI}\right)$, and $e-\gamma \left(\mathrm{Ge}\right(\mathrm{Li}\left)\mathrm{}\right)$ coincidence measurements were made. A value of 1767±10 keV was determined for the ${}_{}{}^{147}{}_{}{}^{}\mathrm{Eu}$ decay energy. $K$-shell internal-conversion coefficients were calculated for most of the observed transitions by intercomparison of the photon intensity data with published conversion-electron intensity data. The existence of previously reported ${}_{}{}^{147}{}_{}{}^{}\mathrm{Sm}$ excited states at 121.3, 197.4, 798.9, 1054, 1077, 1319, 1454, and 1550 keV was confirmed. The experimental information accumulated in this study also indicates new levels at (1007), 1065, 1180, (1228), 1450, 1472, 1656, and (1664) keV. (Levels enclosed in parentheses are only tentatively proposed.) A small percentage of direct ${}_{}{}^{147}{}_{}{}^{}\mathrm{Eu}$ decay to the first three states in ${}_{}{}^{147}{}_{}{}^{}\mathrm{Sm}$ was found to proceed by positron emission. The following ($\frac{K-\mathrm{c}\mathrm{a}\mathrm{p}\mathrm{t}\mathrm{u}\mathrm{r}\mathrm{e}}{{\beta }^{+}}$) ratios were measured: 258±100 (ground state), 257±100 (121.3-keV state), and 302±150 (197.4-keV state).