Clarifying the structure of low-lying states in Br-72

Abstract

The spins and parities of low-lying states in Br72 populated in the β decay of Kr72 have been studied via conversion electron spectroscopy. The measurements were carried out at ISOLDE using a miniorange spectrometer with Si(Li) and HPGe detectors for electrons and γ ray detection. Results of the conversion coefficients corresponding to transitions deexciting 12 levels in Br72 are reported. The multipolarities of the transitions are deduced and the spins and parities of the levels involved are discussed. From the multipolarities of the most intense transitions to the ground state, the spin and parity of the Br72 ground state have been definitely established as 1+. The spin of the 101.2-keV isomeric state is determined to be 3-. The level scheme is compared with mean-field and shell-model calculations and oblate deformation for the Br72 ground state is deduced. No E0 transitions have been found in Br72. E0 transitions in the neighboring isobaric nuclei, Se72 and Ge72, have also been studied