Magnetic and collective rotation in79Br

Excited states of the nucleus ${}^{79}\mathrm{Br}$ were investigated via the reaction ${}^{76}\mathrm{Ge}{(}^{7}\mathrm{Li},4n)$ at a beam energy of 35 MeV. Coincidence data of emitted \ensuremath{\gamma} rays were measured with an arrangement of six EUROBALL CLUSTER detectors. The $E2$ bands built on the ${9/2}^{+}$ and ${3/2}^{\ensuremath{-}}$ states were extended up to $J=37/2$ at $E\ensuremath{\approx}8.8 \mathrm{MeV}.$ The $M1$ band starting with a ${15/2}^{\ensuremath{-}}$ state at 2.6 MeV was observed up to $J=(29/2)$ at $E=6.4 \mathrm{MeV}.$ Crossover $E2$ transitions within this band were observed for the first time. Mean lifetimes of 17 levels were deduced using the Doppler-shift-attenuation method. The $M1$ band can be described within the tilted-axis-cranking model on the basis of the tilted three-quasiparticle configuration $\ensuremath{\pi}{(g}_{9/2}) \ensuremath{\nu}{(g}_{9/2}) \ensuremath{\nu}(\mathrm{fp})$ which has a triaxial shape. This band appears as a mixed case including contributions of both magnetic and collective rotation.