A detailed quantitative experimental investigation of the influence of nuclear deformation on the angular distribution of $\alpha$ particles emitted by oriented nuclei is reported. The favored $\alpha$ transitions in the decay of the deformed nuclei ${}^{221}\mathrm{Fr}$, ${}^{227}\mathrm{Pa}$, and ${}^{229}\mathrm{Pa}$ were studied. In all three cases, very large anisotropies have been observed. The results are in good agreement with calculations based on $\alpha$ particle tunneling through a deformed Coulomb barrier.

• Received 18 December 1998

DOI:https://doi.org/10.1103/PhysRevLett.82.4787