Properties of the rotational bands in Er161

High-spin states in Er161 have been studied experimentally using the Nd150(O16,5n) reaction at a beam energy of 86 MeV. The 5/2+[642], 3/2-[521], and 11/2-[505] bands are extended up to high-spin states, and particularly the α=-1/2 branch of the ground state 3/2-[521] band is revised significantly. The relatively enhanced E1 transitions from the 3/2-[521] band to the 5/2+[642] band are observed. The band properties are analyzed within the framework of a triaxial particle-rotor model, and near-prolate shape and triaxial deformation are proposed to the 3/2-[521] and 5/2+[642] bands, respectively. Signature inversion occurs in the 3/2-[521] band after the band crossing in Er161, and the systematics of the signature inversion associated with the 3/2-[521] configuration are discussed. By analyzing the properties of the relatively enhanced E1 transitions, it is found that the R(E1/E2) values show angular momentum dependence before the band crossing, and these enhanced E1 transitions could be attributed to octupole softness. © 2011 American Physical Society.