Signature inversion and the first observation of a magnetic dipole band in odd-odd rubidium isotopes:82Rb

Abstract

High-spin states in ${}^{82}\mathrm{Rb}$ were studied through the ${}^{68}\mathrm{Zn}{(}^{18}\mathrm{O},p3n)$ reaction at 56 MeV beam energy via a thin target coincidence measurement. The known sequence of positive-parity states built on the ${6}^{+}$ state at 191.3 keV was extended up to spin 14, and signature inversion was observed around spin 11. Above spin 8 the observed properties of this band indicate a rotationlike structure. A new high-lying level sequence connected by $\ensuremath{\Delta}I=1$ transitions was identified. This magnetic dipole sequence is built on a new ${(11}^{\ensuremath{-}})$ level at 2617.3 keV excitation energy which is interpreted as a $\ensuremath{\pi}{(g}_{9/2}{)}^{2}\ensuremath{\bigotimes}\ensuremath{\pi}{(p}_{3/2}{,f}_{5/2})\ensuremath{\bigotimes}\ensuremath{\nu}{g}_{9/2}$ four-quasiparticle state at small quadrupole deformation.