The fission fragment mass and total kinetic energy (TKE) distributions of neutron deficient ${}^{193}\mathrm{Tl}$, populated in the ${}^{28}\mathrm{Si}+{}^{165}\mathrm{Ho}$ and ${}^{34}\mathrm{S}+{}^{159}\mathrm{Tb}$ reactions, have been measured at overlapping excitation energies. By employing a two-dimensional unbinned maximum likelihood fitting procedure, a substantial asymmetric fission fraction was identified across all measured energies with fragment mass centroids pointing toward the influence of deformed shell gaps near $Z\approx 36$. The extracted TKE values consistently cluster into two distinct groups, where the higher TKE associated with the asymmetric mode indicates a more compact scission configuration. While both entrance channels yield compatible asymmetric fractions, the experimental mass widths exhibit a systematic increase below the Coulomb barrier. This enhancement is more pronounced in the ${}^{28}\mathrm{Si} + {}^{165}\mathrm{Ho}$ system, potentially reflecting a “double-deformation” influence from the oblate projectile and highly prolate target. Comparisons with the general description of fission observables (GEF) model show a systematic underprediction of the asymmetric component in ${}^{193}\mathrm{Tl}$, highlighting the potential for continued development of model parameters within this transitional mass region. These results provide critical empirical constraints and demonstrate that while shell effects govern the modal structure, entrance-channel deformations significantly influence the sub-barrier fission dynamics.

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• Fission
• Low & intermediate energy heavy-ion reactions
• Nuclear reactions
• 190 ≤ A ≤ 219