Alignment effects in the medium-spin level structure of Se 78

Abstract

The excited states of Se78 were populated using the Ge76(α,2n) fusion evaporation reaction. The deexcited gamma rays were detected using the Indian National Gamma Array (INGA) spectrometer comprising clover and low-energy photon spectrometer (LEPS) detectors. The ground state band of Se78 has been extended up to Ex = 8.5 MeV and J = 16â ; this excitation regime is very close to the π(1g9/22) crossing frequency. Several newly observed in-band and intraband transitions belonging to the other bands of Se78 have also been placed in the level scheme based on their coincidence relationships. From the newly identified E1 transitions, an enhancement in the B(E1)/B(E2) values with spin has been observed which indicates the onset of octupole correlations in the band structure built on the 3-, 2508-keV state. Persistence of triaxial shape up to the highest observed spin of the ground state band has been observed and the feature of successive 1g9/22 quasiparticle alignments due to protons and neutrons has been unveiled. The consequences arising due to the occurrence of the neutron 1g9/2 quasiparticle alignments in the other observed correlated band structures are also presented. The results are interpreted in terms of total Routhian surface (TRS) calculations and the level structure systematic of the neighboring nuclei. © 2022 American Physical Society.