Alpha-Particle Angular Distributions of At and Rn Isotopes and Their Relation to Nuclear Structure.

Abstract

We report on an extensive on-line nuclear orientation study of the angular distribution of $\ensuremath{\alpha}$ particles emitted in the favored decay of neutron deficient At and Rn nuclei near the $N\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}126$ shell closure. Surprisingly large anisotropies were observed, showing pronounced changes from one isotope to another. Comparing these data with several theoretical models shows that anisotropic $\ensuremath{\alpha}$ emission in favored decays from near-spherical nuclei can well be explained within the shell model, implying that it is mainly determined by the structure of the decaying nucleus.