Energy shifts and broadening of atomic levels near metal surfaces.

Abstract

We present calculations of the lifetime broadening and the shifts of hydrogenlike atomic levels (ground and excited states of H, Li, Na, K, Rb, and Cs) near jellium metal surfaces (Al and Na). The energies and widths of the atomic resonances are obtained from the Schr\odinger equation with use of the complex scaling technique; the electron potential in the surface region is calculated with use of density-functional theory. We find that the energy shifts of the atomic levels are influenced mainly by the properties of the surface potential close to the atom. The widths of the atomic levels, on the other hand, depend on the surface potential in the whole surface region. We show that in order to obtain accurate widths of atomic levels it is important to incorporate nonlocal effects, particularly the image potential. We also find that the widths are strongly influenced by hybridization among the near-degenerate atomic levels. The excited atomic levels shift differently with distance from the surface leading to multiple level crossings. At such positions the hybridization can be strongly enhanced, resulting in states that are oriented towards or away from the surface, with very different lifetimes that may vary in a nonexponential manner with distance from the surface.