High-spin isomer and level structure of 145Sm

Abstract High-spin states of 145 Sm were studied by using the reactions 20 Ne( 136 Xe,α7n), 16 O( 136 Xe,7n), 139 La( 10 B,4n) and 138 Ba( 13 C,6n). The level scheme was extended up to the state at 14.6 MeV. The excitation energy and the spin-parity of the 0.96 μs high-spin isomer were determined to be 8.8 MeV and ( 49 2 + ), respectively. Experimental results were discussed comparing with the deformed independent particle model calculation. High-spin isomers observed in N = 83 isotones were interpreted to be caused by the sudden shape change from near spherical to oblate. The Z = 64 shell gap energy was found to decrease from 2.4 to 2.0 MeV as the proton number decreases from Z = 64 to 61.