Structure of A∼130 nuclei in La-Ce region

Abstract

The variety of shapes and structures, observed in light rare earth A ∼ 130 nuclei, have been discussed in view of different angular momentum coupling schemes and their interplay that comes into effect at high spin. The N = 79 and 80 isotopes in La-Ce region, produced via fusion evaporation reaction, have been studied using the Indian National Gamma Array (INGA) consisting of 18 clover HPGe detectors. Two nearly degenerate ΔI = 1 bands have been observed at high spin of 137 Ce and a triaxial deformation of γ = ±30 • has been assigned to the bands, from the total Routhian surface (TRS) calculations. The high-spin candidates of the yrast band of 138 Ce show signature splitting both in energy and B(M 1)/B(E2) values. The bandcrossing due to the alignment of a pair of h 11/2 proton particles has been conjectured at ω ∼ 0.3 MeV, from the singleparticle Routhians obtained from TRS calculations. Lifetime measurements by Doppler shift attenuation method (DSAM) has been carried out and from the estimated reduced transition probability B(M 1), the ΔI = 1 band in 138 Ce has been characterized as a magnetic rotation (MR) band. The rise in the values of B(M 1), for the higher spin candidates of the band, has been conjectured as the reopening of a different shear at the top of the Band B1. The characteristic of the MR bands in A ∼ 130 region has been discussed in the light of a phenomenological calculation and compared to the MR bands in other mass regions.

Specific features and symmetries for magnetic and chiral bands in nuclei

“…The N=79 and 80 isotopes of La and Ce produced via fusion evaporation reactions have been studied using the Indian National Gamma Array (INGA) consisting of 18 clover HPGe detectors [29]. Indeed, the high-spin states of 137 Ce and 138 Ce were populated via the 130 Te( 12 C,xn) reaction at an energy of 63 MeV, while 136 La was produced in the fusion evaporation reaction 130 Te( 11 B,5nγ) at E beam = 52M eV .…”