A systematic Bayesian analysis of experimentally measured nuclear level densities for ${}^{204,206,207,208}\mathrm{Bi}$ and ${}^{209}\mathrm{Po}$ nuclei has been performed to investigate the damping of shell effects with increasing excitation energy. The analysis indicates high shell-damping rates (${\gamma }_0$ = $0.{59}_{-0.10}^{+0.22}, 0.{53}_{-0.06}^{+0.16}$, and $0.{49}_{-0.07}^{+0.20} {\mathrm{MeV}}^{-1}$) in neutron-deficient bismuth nuclei (${}^{204}\mathrm{Bi},{}^{206}\mathrm{Bi}$, and ${}^{207}\mathrm{Bi}$), implying a rapid attenuation of shell effects as the excitation energy increases. Systematic investigation incorporating different treatments of pairing correlations and spin cutoff prescriptions demonstrate that the deduced shell-damping rates have minimal model dependence. These findings provide valuable insight into the excitation energy dependence of shell structure near the closed-shell nuclei.

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• Level densities
• Nuclear fusion
• Nuclear reactions
• 190 ≤ A ≤ 219
• Bayesian methods