The decay of Eu 150 (13 h) and Eu 150 (≈ 5 y)

Abstract

The decay of the two isomeriic states of Eu 150 has been studied using spectrometers and coincidence and directional correlation techniques. In addition, the gamma-ray spectrum of 5 y Eu 150 has been investigated with a lithium-drifted germanium detector. The nucleus Eu 150 (13 h) decays to both Sm 150 and Gd 150. The decay to Sm 150 proceeds via electron capture and a 1242 keV position branch (0.3%) to the ground state keV.ure branches to levels at 334 (2 +), 740 (0 +), 1047 (2 +), 1165 (2 +), 1256 (0 +) and 1970 (1 −, 2 +) keV. A level at 1764 keV is possible. Spin and parity assignments were established by internal conversion coefficient and gamma-gamma directional correlation measurements. Gamma-ray transitions of the following energies (and relative intensities) were observed: 334(8.3), 406(6.2), 714(0.4), 831(0.9), 922(0.8), 1165(0.7), 1230(0.2), 1636(0.14) and 1970(0.3) keV. A 1010 keV β − branch (87% of all decay) proceeds to the ground state of Gd 150. The most likely assignment for the short-lived Eu 150 is 1 − or possibly 0 −. The decay of Eu 150 (≈ 5 y) proceeds to levels in Sm 150 at 334(2 +), 773(4 +), 1072(3 ±), 1357(5, 3), 1505, 1642, 1822, 1973, 2021 and 2120 keV. A level at 1278 keV is also possible. Gamma-ray transitions of the following energies (and relative intensities) were observed in the decay: 298(< 1), 334(100), 439(89), 506(5.4), 516(1.9), 584(60), 738(2..9), 750(8.8), 831, 869(4.8), 104((9.0), 1171(3.0), 1248(4.8), 1309(1.6), 1347(4.5), 1488(2.2) and 1639(1.3) keV. In addition foeveral other weaker transitions were observed. Gamma-gamma directional correlations were measured for several prominent cascades. The observed log ft values for the electron-capture branches are most consistent with an assignment of 5 − or 4 − for the long-lived Eu 150.