Low-spin excitations in 89Br populated in β−decay of 89Se

Abstract

Low-spin, excited states of the 89Br nucleus, populated in β− decay of 89Se have been studied for the first time. The 89Se nuclei were produced in proton-induced fission of natural thorium using the IGISOL facility and separated using a dipole magnet and the coupled JYFLTRAP Penning trap. Gamma radiation following the β− decay of 89Se was measured with an array of high-resolution germanium detectors. Levels scheme of 89Br was extended by 12 new levels and 31 new γ transitions. Spin-parity (3/2+) has been proposed for the ground state of the 89Se mother nucleus, replacing the (5/2+) assignment reported in data bases. The observed Gamow-Teller β− transition to the 1754.5-keV level indicates a πg9/2-based configuration. The level scheme of 89Br has been compared to large scale shell-model calculations. Excitations based on πp3/2 and πf5/2 single-particle levels as well as their anomalous coupling are proposed to explain the low-energy excitation scheme of 89Br.