In-beam measurement ofE0matrix element inSe72andGe72

A 0 + state in ${}_{}{}^{72}{}_{}{}^{}\mathrm{Se}$ at 936 keV has been identified through in-beam measurements with ${}_{}{}^{70}{}_{}{}^{}\mathrm{Ge}(\alpha ,2n){}_{}{}^{72}{}_{}{}^{}\mathrm{Se}$. The beam-related time distribution of conversion electrons from the 936-keV $E0\mathrm{}$ transition yields a half-life of 19.3±0.4 ns. With a ${}_{}{}^{72}{}_{}{}^{}\mathrm{Ge}$ target and an $\alpha$-beam sweeper the half-life of the 690-keV $E0\mathrm{}$ transition in ${}_{}{}^{72}{}_{}{}^{}\mathrm{Ge}$ was 404±45 ns. For both transitions identification of the emitting nucleus was obtained from the energy separation of the $K$ and $L$ electrons. The $\frac{K}{L}$ intensity ratio was intermediate between the theoretical results of Hager and Seltzer and those of Church and Weneser. The reduced $E0\mathrm{}$ nuclear matrix elements are $\rho =(0.304\mathrm{}\pm 0.003)(1-5.01\times {10}^{-3\mathrm{}}f)$ and $\rho =0.095\mathrm{}\pm 0.005$ for ${}_{}{}^{72}{}_{}{}^{}\mathrm{Se}$ and ${}_{}{}^{72}{}_{}{}^{}\mathrm{Ge}$, respectively, which are 0.77 (for $f\lesssim 40$) and 0.24, respectively, of Wilkinson's suggested single-particle unit for $E0\mathrm{}$ matrix elements. The $f$ is the 0′→2 enhancement.