Decay ofLa136andLa134

Abstract

Sources of 9.87-min ${}_{}{}^{136}{}_{}{}^{}\mathrm{La}$ and 6.82-min ${}_{}{}^{134}{}_{}{}^{}\mathrm{La}$ were made by the ($p,n$) reaction on enriched ${}_{}{}^{136}{}_{}{}^{}\mathrm{Ba}$ and ${}_{}{}^{134}{}_{}{}^{}\mathrm{Ba}$. A 20-cc Ge(Li) detector was used to observe the $\gamma$ rays emitted by these sources. The energies in keV (with relative intensities in parentheses) of $\gamma$ rays emitted in the decay of ${}_{}{}^{136}{}_{}{}^{}\mathrm{La}$ are 760.4(14.3), 818.5(100), 1019.1(5.6), 1261.7(1.3), 1310.5(4.5), 1322.5(13.0), 1497.1(2.1), 2127.7(1.7), and annihilation radiation (3090). The energies in keV (with relative intensities in parentheses) of $\gamma$ rays emitted in the decay of ${}_{}{}^{134}{}_{}{}^{}\mathrm{La}$ are 563.5(6.7) 604.7(100), 1168.9(2.6), 1211.0(2.4), 1321.1(2.4), 1424.1(3.9), 1482.4(2.3), 1555.0(8.6), 1731.7(4.9), 1960.4(2.0), 1995.2(1.4), 2088.6(0.8), and annihilation radiation (2200). These results are consistent with the existence of excited states of ${}_{}{}^{136}{}_{}{}^{}\mathrm{Ba}$ at 818.5, 1578.9, 2080.2, 2128.5, 2141.0, and 2315.6 keV, and excited states of ${}_{}{}^{134}{}_{}{}^{}\mathrm{Ba}$ at 604.7, 1168.2, 2159.7, 2336.4, 2489.3, 2565.1, 2599.9, and 2693.3 keV.