Investigation of the low- and medium-spin level structure in As77

The low- and medium-spin level structure of As77 nucleus has been investigated using the Ge76(α,p2n) fusion evaporation reaction and the standard in-beam γ ray spectroscopic technique. The deexciting γ rays were detected with the Indian National Gamma Array spectrometer comprising Clover and LEPS detectors. The previously known 9/2+ yrast positive-parity band, based on the π(g9/2) configuration, has been extended to the excitation energy of Ex≈7.5 MeV with Jπ=(33/2+). An extension of the high-lying negative-parity band, based on the π[(g9/2)]⊗ν[(g9/2)(fp)] configuration, has been made up to Ex≈5.1 MeV, Jπ=(25/2−). The yrast positive-parity α=−1/2 signature partner band has newly been identified and the occurrence of large signature splitting associated with the partner bands have been observed. A quasi-γ vibrational band structure built on the nonyrast 13/2+ state has also newly been established. The experimental findings have been interpreted on the basis of the predicted results from the total Routhian surface, particle plus triaxial-rotor model, and shell-model calculations. The band crossing phenomena correlated to the ν(g9/2) alignment and the perseverance of triaxial shape up to the highest observed excitation regime of the 9/2+ yrast positive-parity band have been discussed. The evidence for the possible onset of the stapler-like mechanism prevailing in the high-lying negative-parity band structure are presented.7 MoreReceived 1 February 2023Accepted 9 June 2023DOI:https://doi.org/10.1103/PhysRevC.107.064320©2023 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasNuclear fusionNuclear structure & decaysProperties59 ≤ A ≤ 89TechniquesNuclear data analysis & compilationAccelerators & BeamsNuclear Physics