nDependence ofl-Changing Collisions betweenHe+Ions and Na

Abstract

$l$-changing collisions were observed in a crossed ${\mathrm{He}}^{+}$-ion/Na-Rydberg-atom beam experiment. Transitions $\mathrm{nd}\to n(l>~3)$ induced in Na by ion impact at 450 and 600 eV were studied for $n=20-34\mathrm{}$. Cross sections vary approximately as $n^5$ and have magnitudes of order ${10}^8$ ${\mathrm{\AA }}^2$, a few hundred times the geometric cross section of the Rydberg atoms.