Lifetimes of First 2+ and 4+ States ofPt192and Some Systematics ofE2Transitions in Even-Even Nuclei

Abstract

The mean lifetimes of the first 2+ (316-keV) and 4+ (785-keV) states of ${}_{}{}^{192}{}_{}{}^{}\mathrm{Pt}$ have been measured using the delayed-coincidence method. The results are ${\tau }_m\mathrm{}(2+)=(5.1\mathrm{}\pm 0.4)\times {10}^{-11\mathrm{}}$ sec and ${\tau }_m\mathrm{}(4+)=(1.7\mathrm{}\pm 0.3)\times {10}^{-11\mathrm{}}$ sec. The 2→0 transition is enhanced by a factor 69 and the 4→2 by a factor 31 relative to the single-particle estimate. Thus $\frac{B(E2; 4\to 2)}{B(E2; 2\to 0)}=0.45\mathrm{}\pm 0.10$. The systematics of the 2+ states and $B\left(E2\mathrm{}\right)\mathrm{}$ values for nuclei with $170\le A\le 210$ are presented. In addition, a compilation of measured ratios $\frac{B(E2; 4\to 2)}{B(E2; 2\to 0)}$ for all nuclei is given. Comparison with these systematics indicate that in ${}_{}{}^{192}{}_{}{}^{}\mathrm{Pt}$ the 2→0 transition is unusually fast and $\frac{B(E2; 4\to 2)}{B(E2; 2\to 0)}$ is small. Studies of the conversion electron spectrum of ${}_{}{}^{192}{}_{}{}^{}\mathrm{Pt}$ show that the previous assignment of a 4→2′ transition is incorrect.