Evidence for deformed states in 75Br

The excited states in ⁷⁵Br have been studied via the reactions ⁷⁴Se(p, γ), ⁷⁴Se(d, n), ⁷⁴Se(³He, pn) and ⁷⁴Se(α, p2n) by using in-beam γ-ray spectroscopy. In addition to measurements of γ-γ coincidences, excitation functions and angular distributions of γ-rays, ns lifetime measurements have also been carried out. As a result 19 levels have been identified up to spin ($\text{17}\text{2}$) and excitation energies up to 2.6 MeV. The B(E2) value of 88 W.u. derived for the 88.4 keV γ-ray indicates strong collectivity within a positive-parity band. A comparison of the excitation energies of the unique-parity states in ⁷⁵Br and ⁷⁷Br with those in ¹⁵³Tb and ¹⁵⁵Tb reveals that the average deformation increases when going from ⁷⁷Br (N = 42) to ⁷⁵Br (N = 40).