Experimental observation of high spin states in 135La nucleus

High spin states of 135La have been experimentally studied by using 128Te(10B, 3n)135La reaction at 46 MeV beam energy. Based on the γ-γ coincidence relationships, relative intensities and ADO ratios, a level scheme of 135La has been established. Both signature components of the πh11/2 negative-parity band and a band crossing at ℎω≅0.40 MeV were observed. In view of the systematics of the N=78 isotones, this backbending is proposed to be caused by the alignment of a pair of πh11/2 protons. The πh11/2 protons drive the nuclear core towards γ≅0 degree, the collective prolate shape. In addition, a ΔI=1 negative-parity band with strong M1 transitions and a very small signature splitting was observed. Comparing with the systematic features of ΔI=1 bands in neighboring odd-proton nuclei in this mass region, the πh11/2 direct x (νh11/2)2 configuration was assigned to the ΔI=1 bands of 135La. The alignment of the h11/2 neutron pair drives the nuclear core towards γ≅-60 degree, the collective oblate shape