Size quantization effects in atomic level broadening near thin metallic films

The broadening of atomic levels near thin metallic films is studied theoretically within the fixed-atom approximation. First-order level widths are calculated by using a Jennings-type jellium potential to describe the electronic states of the film, and hydrogenic wave functions in parabolic (Stark) representation for the atomic orbitals. In the parabolic representation, hybridization effects due to the long-range image-charge interactions are taken into account. Size quantization in the growth direction of the film gives rise to characteristic structures in level widths, atomic occupation probabilities, and transition distances as a function of the film thickness. Details of this structure depend on the orientation of the Stark orbitals with respect to the film and can be related to the dependence of transition matrix elements on the active electron's wave vector component parallel to the surface for the case of a semi-infinite metal. The large variation of the calculated transition distances with the film thickness may result in observable effects in atomic interactions with thin films.