Study of Medium-Mass Odd-Odd Nuclei Close to the N = Z Line

The β⁺ decay of the N = Z odd-odd nuclei ⁶²Ga and ⁷⁰Br has been investigated at the on-line mass separator of GSI Darmstadt. The nuclei were produced by using beams of ³⁶Ar on ²⁸Si and ⁴⁰Ca targets. In the decay of ⁶²Ga, besides an intense 511 keV annihilation peak, the 954 keV 2⁺ → 0⁺ transition in ⁶²Zn has been observed weakly, whereas many γ transitions with a half-life of 2.2(1) s have been identified in the ⁷⁰Br → ⁷⁰Se decay. Based on the observed population of levels in ⁷⁰Se, spin and parity of 9⁺ are assigned to the β-decaying state in ⁷⁰Br. The occurrence of such a high-spin state is interpreted as arising from the (π9/2⁺[404], ν9/2⁺[404])) intruder configuration at oblate deformation.