Isomer Spectroscopy in Th-216(90)126 and the magicity of U-218(92)126 - art. no. 072501

Excited states in Th-216 were investigated via prompt and delayed gamma dec ays and the recoil-decay tagging method. The decay schemes of the I-pi = (8 (+)), t(1/2) = 128(8) mus, the I-pi = (11(-)), t(1/2) = 615(55) ns, and the I-pi = (14(+)), t(1/2) greater than or equal to 130 ns isomers were establ ished. The configuration pih(9/2)f(7/2) is assigned to the I-pi = (8(+)) is omer, which implies that the h(9/2) and f(7/2) states are nearly degenerate . This is ascribed to increased binding of the f(7/2) orbital by its coupli ng to a low-lying I-pi = (3(-)) state at E-x = 1687 keV. The role of octupo le and pairing correlations for a Z = 92 shell closure prediction is discus sed on the basis of shell model calculations.