The high-spin states of ${}_{}{}^{74}{}_{}{}^{}\mathrm{Br}$ were studied via the ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}$${(}^{32}$S,αpn${)}^{74}$Br and the ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$${(}^{19}$F,2pn${)}^{74}$Br fusion-evaporation reactions at energies of 105 and 62 MeV, respectively, using the Florida State University Tandem LINAC. γ-γ coincidence arrays were produced using four Compton-suppressed Ge detectors. Two independent groups of γ rays were studied–one of positive parity and one of negative parity, both of which appear to be based on an isomeric $4^{\mathrm{}(+)\mathrm{}}$ state. Lifetimes were measured using both the Doppler-shift attenuation and recoil-distance methods. A cranking-model analysis of the bands shows that the kinematic and dynamic moments of inertia for the bands are rather similar and fairly constant for high spins with values of (20–23)${\mathrm{ħ}}^2$/MeV. A phase reversal occurs in the signature splitting in the yrast band around spin 9 which is related to the quasiparticle alignments. The lifetimes imply an average axial quadrupole deformation of 0.37 in the yrast band and 0.34 in the negative-parity band. These deformations are close to those predicted by Hartree-Fock-Bogolyubov cranking calculations.

• Received 20 July 1990

DOI:https://doi.org/10.1103/PhysRevC.43.470