We present a theoretical description of proton radioactivity in ${}^{149}\mathrm{Lu}$, the most oblate deformed proton emitter known, by combining a deformed microscopic optical potential derived from ab initio nuclear matter calculations with the Wentzel-Kramers-Brillouin penetration probabilities and the assault frequency of the emitted proton estimated through a new harmonic-oscillator-inspired scheme. We predict a novel angular-dependent phenomenon unprecedented in spherical proton emitters: the disappearance of classically allowed regions at small polar angles $(\theta \le {21}^{\circ })$. Our framework yields a half-life $T_{1/2}={467}_{-108}^{+143}\mathrm{ns}$ for ${}^{149}\mathrm{Lu}$, in excellent agreement within uncertainties with the experimental value ${450}_{-100}^{+170}\mathrm{ns}$. Deformation analysis rigorously excludes configurations with $|{\beta }_2|\ge 0.32$. Extensions to ${}^{150,151}\mathrm{Lu}$ and their isomers also achieve excellent agreement with experimental half-life data. We further predict ${}^{148}\mathrm{Lu}$ as another highly oblate $({\beta }_2=-0.166)$ proton emitter with a half-life $T_{1/2}=4.42\mathrm{ns}$. This work validates deformed microscopic optical potentials as a robust predictive tool for drip-line proton emitters and provides quantitative evidence for deformation effects in exotic decays.

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• Lifetimes & widths
• Nuclear many-body theory
• Nuclear matter
• Proton emission
• Rare & new isotopes
• 90 ≤ A ≤ 149
• Ab initio calculations