HIGH-SPIN ISOMER AND LEVEL STRUCTURE OF SM-145

High-spin states of Sm-145 were studied by using the reactions Ne-20(X e-136,alpha 7n), O-16(Xe-136,7n), La-139(B-10,4n) and Ba-138(C-13,6n). The level scheme was extended up to the state at 14.6 MeV, The excita tion energy and the spin-parity of the 0.96 mu s high-spin isomer were determined to be 8.8 MeV and (49/2(+)), respectively. Experimental re sults 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 spherica l 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. (C) 199 7 Elsevier Science B.V.