Alpha-Particle Angular Distributions with Respect to Spin Direction

Abstract

Angular distribution of alpha particles with respect to the spin direction of residual nuclei from fusion of 176-MeV $^{20}\mathrm{Ne}$ with $^{150}\mathrm{Nd}$ has been measured with the spin spectrometer. Below the Coulomb barrier, the ratio of the 90\ifmmode^\circ\else\textdegree\fi{} to 0\ifmmode^\circ\else\textdegree\fi{} yields with respect to spin direction increases with decreasing ${E}_{\ensuremath{\alpha}}$. This effect is not shown by a statistical-model calculation using penetrabilities for spherical potentials, which suggests that the $\ensuremath{\alpha}$-mitting nuclei are deformed with their longest axis perpendicular to the spin direction. If so, the deformation increases as the spin rises from \ensuremath{\sim} 34 to $64\ensuremath{\hbar}$.