Possible chirality in the doubly-odd Tl198 nucleus: Residual interaction at play

A candidate for chiral bands was found in Tl198 for the first time in a mass region of oblate (or nonaxial with γ≥30°) 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 γ~44° agrees very well with all the experimental observations. Furthermore, considerable energy staggering for both partner bands was calculated for this πh9/2 νi13/2-1 configuration at γ~30°, suggesting that chiral bands may have substantial energy staggering.