Band structures extending to very high spin inXe126

Abstract

High-spin states in $^{126}\mathrm{Xe}$ have been populated in the $^{82}\mathrm{Se}$($^{48}\mathrm{Ca}$,4$n$)$^{126}\mathrm{Xe}$ reaction in two experiments, one at the VIVITRON accelerator in Strasbourg using the Euroball detector array, and a subsequent one with ATLAS at Argonne using the Gammasphere Ge-detector array. Levels and assignments made previously for $^{126}\mathrm{Xe}$ up to $I=20$ have been confirmed and extended. Four regular bands extending to a spin of almost $I=60$, which are interpreted as two pairs of signature partners with opposite parity, are identified for the first time. The \ensuremath{\alpha} = 0 partner of each pair is connected to the lower-lying levels, whereas the two \ensuremath{\alpha} = 1 partners remain floating. A fractional Doppler shift analysis of transitions in the strongest populated $(\ensuremath{\pi},\ensuremath{\alpha})=(\ensuremath{-},0)$ band provides a value of ${5.2}_{0.5}^{0.4}$ b for the transition quadrupole moment, which can be related to a minimum in the potential-energy surface calculated by the ULTIMATE CRANKER cranked shell-model code at $\ensuremath{\epsilon}\ensuremath{\approx}0.35$ and $\ensuremath{\gamma}\ensuremath{\approx}{5}^{\ifmmode^\circ\else\textdegree\fi{}}$. The four lowest bands calculated for this minimum compare well with the two signature pairs experimentally observed over a wide spin range. A sharp upbend at $\ensuremath{\hbar}\ensuremath{\omega}~1170$ keV is interpreted as a crossing with a band involving the ${j}_{15/2}$ neutron orbital, for which pairing correlations are expected to be totally quenched. The four long bands extend to within \ensuremath{\sim}5 spin units of a crossing with an yrast line defined by calculated hyperdeformed transitions and will serve as important stepping stones into the spin region beyond 60\ensuremath{\Elzxh} for future experiments.