Return of backbending in Tm169 and the effect of the N=98 deformed shell gap

The high spin excited states of Tm-169 have been studied via the Tm-169(S-32, S-32') 1(69)Tm(*) reaction at a beam energy of 164 MeV. The gamma rays were detected using an array of 19 Compton-suppressed clover HPGe detectors. The band based on the [411]1/2(+) Nilsson orbital has been extended to observe the band crossing for the first time in this nucleus. A sharp backbending, similar to Tm-165, is observed in this nucleus which is in complete contrast with its immediate neighbor Tm-167. The data were interpreted in the cranked shell model approach by calculating the total Routhian surfaces, crossing frequencies, and the interaction strengths for these nuclei which are in excellent agreement with the experimental data. It is suggested that the N = 98 deformed shell gap has larger effect in determining the nature of alignment than its shape driving effect.