BA135(N,GAMMA) REACTION AND LEVEL STRUCTURE OF BA136

The γ rays from the Ba135(nth, γ)Ba136 reaction have been studied in singles and in coincidence with a 9-cm3 Ge(Li) detector and a Ge(Li)-NaI detector combination. Of the 78 γ rays assigned to Ba136, 16 have been identified as primary transitions deexciting the compound nucleus. These primary γ rays have energies (in keV) and relative intensities [I(818 keV)=100] as follows: 9106.5±1.3 (2.9), 8288.2±0.8 (1.8), 7554.3±1.0 (0.24), 7526.6±2.0 (0.07), 7026.4±0.7 (0.7), 6978.2±0.7 (0.2), 6707.4±0.8 (0.3), 6574.9±0.6 (0.5), 6087.4±0.5 (0.3), 6063.5±0.4 (3.5), 5673.2±0.6 (0.4), 5601.8±0.6 (1.0), 5415.8±0.5 (2.2), 5340.3±0.7 (0.2), 5311.9±0.6 (3.7), and 5181.5±2.6 (0.9). These data, together with the information obtained from the coincidence studies and from previous decay scheme and neutron capture γ-ray studies, establish levels in Ba136 with energies 818.6±0.2, 1550.5±0.4, 1579.2±0.4, 1866.3±0.4, 2030.0±0.5, 2053.5±0.6, 2079.9±0.6, 2128.3±0.8, 2139.6±0.6, 2206.3±0.5, 2398.6±0.3, 2531.8±0.5, 3019.9±0.5, 3043.6±1.4, 3433.2±0.5, 3504.9±1.1, 3690.8±1.5, 3767.1±1.0, 3795.4±0.9, and 3925.7±1.2 keV. The neutron separation energy was found to be 9106.4±0.8 keV. The level scheme of Ba136 is discussed. The branching ratio B(E2; 2+′→0+)B(E2; 2+′→2+) was measured and found to be 0.029±0.006, in agreement with measured values of the same quantity for other near-harmonic nuclei. © 1969 The American Physical Society.