Deformed band structures at high spin in Tl200

High-spin band structures of $^{200}\mathrm{Tl}$ have been studied by $\ensuremath{\gamma}$-ray spectroscopic methods using the $^{198}\mathrm{Pt}(^{7}\mathrm{Li},5n)^{200}\mathrm{Tl}$ reaction at 45 MeV of beam energy. The level scheme of $^{200}\mathrm{Tl}$ has been extended significantly and several new band structures have been established with the observation of 60 new transitions. The $\ensuremath{\pi}{h}_{9/2}\ensuremath{\bigotimes}\ensuremath{\nu}{i}_{13/2}$ oblate band has been extended beyond the particle alignment frequencies. The band structures and the other excited states have been compared with the neighboring odd-odd Tl isotopes. Total Routhian surface calculations have been performed to study the deformation and shape changes as a function of spin in this nucleus. These calculations could reproduce the particle alignment frequency and suggest that the neutron pair alignment in $\ensuremath{\nu}{i}_{13/2}$ orbital induces $\ensuremath{\gamma}$ softness in $^{200}\mathrm{Tl}$.