Interaction of Rydberg atoms with a metal surface in the presence of an external electric field

The behavior of Rydberg atoms near metal surfaces in the presence of an external electric field has been examined theoretically to evaluate their potential use as an experimental probe of electron tunneling processes at surfaces. These ab initio calculations reveal strong hybridization that leads to a shift and broadening of the Rydberg levels that depend sensitively on the atom-surface separation and the strength of the applied electric field. A range of external fields exists, however, for which the Rydberg atoms ionize at sufficiently large atom-surface separations that, even in the presence of image charge attraction, the resulting positive ions can escape the surface and provide an experimentally observable signal. {} 1996 The American Physical Society.