形变双奇核^(178)Ir转动带能级的旋称反转

Signature Inversion in the Rotational Bands of Odd-Odd ^(178)Ir

利用１５２Ｓｍ（３１Ｐ，５ｎγ）１７８Ｉｒ反应产生并研究了双奇核１７８Ｉｒ的高自旋态．实验中进行了１７８Ｉｒ核的在束 γ测量，包括γ射线的激发函数测量、Ｘ－γ和γ－γ符合测量．首次建立了双奇核１７８Ｉｒ基于πｈ９／２νｉ１３／２和πｈ１１／２νｉ１３／２准粒子组态上的转动带能级纲图．发现在低自旋区，两个转动带能级均出现旋称反转．对此核区半退耦带的旋称反转作了简要的分析和讨论．

High-spin states in 178Ir have been produced and studied via the 152Sm(30p,5nγ) 178 Ir reaction. In-beam γ rays were measured including the excitation functions at 150 , 155, 160, 165 and 170 MeV beam energies,K X-γ and γ-γ coincidences at 160 MeV. According to the band structure characteristics and the deduced intra-band B (M1)/B (E2) ratios, two rotational bands are identified for the first time and assigned to be associated with the πh9/2νi13/2 and the πh11/2νi13/2 quasiparticle configurations respectively. Low-spin signature inversion in bob bands has been confirmed hased on the observation of signature crossing at Ic = 21 h for the πh9/2νi13/2, semidecoupled band and at Ic = 16 h for the πh11/2νi13/2 strongly coupled band, respectively. Systematics of the signature inversion has been discussed for the semidecoupled bands in the A= 160-180 mass region and some regularities are proposed concerning the crossing spins with variation of mass. The signature splitting in the πh11/2νi13/2 band of 178Ir is smaller than that in the similar band of 176Re; this trend is opposite to the predictions based on the projected shell model.