Anisotropic Alpha Emission from On-Line-Separated Isotopes

Abstract

A systematic on-line nuclear-orientation study of heavy isotopes by use of anisotropic $\ensuremath{\alpha}$ emission is reported for the first time. The anisotropies recorded for $^{199}\mathrm{At}$, $^{201}\mathrm{At}$, and $^{203}\mathrm{At}$ are remarkably pronounced and strongly varying. At lower neutron number the $\ensuremath{\alpha}$ particles are more preferentially emitted perpendicularly to the nuclear-spin direction. This may be interpreted in terms of the high sensitivity of the $\ensuremath{\alpha}$-emission probability to changes in the nuclear shape.