Possible chirality in the doubly-oddTl198nucleus: Residual interaction at play

Abstract

A candidate for chiral bands was found in $^{198}\mathrm{Tl}$ for the first time in a mass region of oblate (or nonaxial with $\ensuremath{\gamma}\ensuremath{\geqslant}{30}^{\ifmmode^\circ\else\textdegree\fi{}}$) deformed nuclei. Two bands show very similar quasiparticle alignments, moments of inertia, and $B(M1)/B(E2)$ ratios. They have a relative excitation energy of about 500 keV and different patterns of energy staggering. Calculations using the two-quasiparticle-plus-triaxial-rotor model with residual proton-neutron interaction included show that a triaxial deformation with $\ensuremath{\gamma}~{44}^{\ifmmode^\circ\else\textdegree\fi{}}$ agrees very well with all the experimental observations. Furthermore, considerable energy staggering for both partner bands was calculated for this $\ensuremath{\pi}{h}_{9/2}\ensuremath{\bigotimes}\ensuremath{\nu}{i}_{13/2}^{\ensuremath{-}1}$ configuration at $\ensuremath{\gamma}~{30}^{\ifmmode^\circ\else\textdegree\fi{}}$, suggesting that chiral bands may have substantial energy staggering.