Revealing multiple band structures in Xe-131 from alpha-induced reactions

The excited states in the transitional nucleus Xe-131 have been populated by using alpha-induced fusion-evaporation reaction and the de-exciting gamma rays were detected with the Compton suppressed clover detector setup of the Indian National Gamma Array coupled to digital data acquisition system. The existing level structure of Xe-131 has been significantly extended with the observation and placement of 72 new gamma-ray transitions. The use of light-ion (alpha) beam helped to identify several new band structures in Xe-131 with different quasiparticle (qp) configurations. The multipolarities of the observed gamma rays have been determined on the basis of the directional correlation from oriented states ratio and polarization asymmetry measurements. The gamma-rast negative-parity band has been confirmed up to 35/2(-) spin and the highly nonyrast signature partner of this band has been identified for the first time. The positive-parity band, based on the 3/2+ ground state, has been extended up to 3/2(+) with the observation of a signature inversion, which signifies a pair of particle alignment around the spin of 15/2 (h) over bar. A dipole band, consisting of M1 transitions has been identified and assigned a 5-qp configuration. A new band structure built on a 3-qp 23/2(+) state has been observed with a large signature splitting. A comparison in the isotopic and isotonic chains reveals the transitional nature of the N = 77 nuclei. Total Routhian surface calculations have been performed to understand the structure of Xe-131 associated with different configurations.