Three-quasiparticle excitations inBr77

Excited states in ${}_{}{}^{77}{}_{}{}^{}\mathrm{Br}$ were investigated via the reactions ${}_{}{}^{75}{}_{}{}^{}\mathrm{As}$(α,2n${)}^{77}$Br and ${}_{}{}^{73,74}{}_{}{}^{}\mathrm{Ge}$ ${(}^7$Li,xn${)}^{77}$Br at beam energies of 27 and 35 MeV, respectively. On the basis of coincidence and angular distribution data of the γ rays the known level sequences of positive and negative parity were extended to tentative spins of 25/2ħ, and a new decay sequence beginning at spin and parity of (17/$2^{\mathrm{-}}$) was found. This new sequence is discussed in terms of the 3-quasiparticle configuration (π${\mathit{g}}_{9/2}$⊗ν${\mathit{g}}_{9/2}$⊗ν (${\mathit{p}}_{1/2}$,${\mathit{p}}_{3/2}$,${\mathit{f}}_{5/2}$)). Moreover, the irregularity found in the moments of inertia at ħω≊0.4 MeV for the negative-parity band is attributed to a ${\mathit{g}}_{9/2}$ quasiproton alignment.