\(\gamma \)-Ray spectroscopy above the 9\(^+\) isomeric state in the N = Z nucleus \(^{66}\)As

Abstract

Excited states above the \(9^+\) isomer in the odd-odd N = Z nucleus \(^{66}\)As were studied by employing the \(^{40}\)Ca(\(^{28}\)Si, pn) fusion-evaporation reaction at the Accelerator Laboratory of the University of Jyväskylä, Finland. A key method in this study was the use of conversion electrons emitted in the de-excitation of the isomeric state in \(^{66}\)As as a tag for prompt \(\gamma \) rays. Several new states have been added to the \(^{66}\)As level scheme, which was extended up to a tentative spin of 23\(\hbar \). The previously reported even-spin yrast band has been reassigned to have odd spin values. The odd-spin states above the \(9^+\) isomer are compared with shell-model calculations using the jj44b and JUN45 interactions. Additionally, the recoil-\(\beta \) tagging efficiency of the recently developed scintillator detector named Tuike has been determined experimentally for the first time.