Resonant Rydberg-Atom-Rydberg-Atom Collisions

Abstract

We have observed the sharply resonant enhancement of the cross section of the collision process $ns+ns\to np+(n-1\mathrm{})p$ between two $\mathrm{Na}ns$ ($16<~n<~27$) atoms which occurs when the levels are shifted by an electric field so that the $ns$ level lies midway between the two $p$ states. The widths of the collisional resonances scale as $n^{-2\mathrm{}}$ and the magnitudes of the cross sections as $n^4$, with values of 0.5 GHz and 8×${10}^8$ ${\mathrm{\AA }}^2$ for the $20s$ state. These results are in good agreement with calculations based on the long-range dipole-dipole interaction between the two atoms.