Proton radioactivity in deformed nuclei with microscopic optical potential: A novel angular-dependent emission mechanism in the nanosecond-lived ${}^{149}$Lu

We present a theoretical description of proton radioactivity in 149Lu, 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 $T_{1\mathrm{/}2}=467_{-108}^{+143}$ ns for 149Lu, in excellent agreement within uncertainties with the experimental value $450_{-100}^{+170}$ ns. Deformation analysis rigorously excludes configurations with $\mathrm{\mid }{\beta }_2\mathrm{\mid }\ge 0.32$. Extensions to 150, 151Lu and their isomers also achieve excellent agreement with experimental half-life data. We further predict 148Lu as another highly oblate $({\beta }_2=-0.166)$ proton emitter with a half-life $T_{1\mathrm{/}2}=4.42$ 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.