Rotational bands and signature inversion in odd-oddRe172

Abstract

High-spin states in the odd-odd $^{172}\mathrm{Re}$ have been investigated via the $^{149}\mathrm{Sm}(^{27}\mathrm{Al},4n\ensuremath{\gamma})^{172}\mathrm{Re}$ reaction through excitation functions, $x\text{\ensuremath{-}}\ensuremath{\gamma}$ and $\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}$ coincidence measurements. A level scheme consisting of three rotational bands has been identified for the first time extending the high-spin studies of $A\ensuremath{\sim}160$ odd-odd nuclei to the currently lightest rhenium isotope. The three bands have been assigned to be built on the $\ensuremath{\pi}{h}_{11∕2}\ensuremath{\bigotimes}\ensuremath{\nu}{i}_{13∕2}$, $\ensuremath{\pi}{h}_{9∕2}\ensuremath{\bigotimes}\ensuremath{\nu}{i}_{13∕2}$, and $\ensuremath{\pi}1∕{2}^{\ensuremath{-}}[541]\ensuremath{\bigotimes}\ensuremath{\nu}1∕{2}^{\ensuremath{-}}[521]$ configurations according to their rotational properties in quasiparticle alignments, signature splitting, in-band $B(M1)∕B(E2)$ ratios, level spacing systematics, band crossing frequencies, as well as the existing knowledge in neighboring nuclei. Low-spin signature inversion has been confirmed in the first two bands due to the observation of signature crossing at high-spin states. The general features of inversion phenomenon in the semidecoupled bands are presented and discussed with reference to theoretical calculations of two quasiparticle plus rotor model including $p\text{\ensuremath{-}}n$ interactions.