Size quantization effects in atomic level broadening near thin metallic films

The broadening of atomic levels near thin metallic films is studied theoret ically within the fixed-atom approximation. First-order level widths are ca lculated by using a Jennings-type jellium potential to describe the electro nic states of the film, and hydrogenic wave functions in parabolic (Stark) representation for the atomic orbitals. In the parabolic representation, hy bridization effects due to the long-range image-charge interactions are tak en into account. Size quantization in the growth direction of the film give s rise to characteristic structures in level widths, atomic occupation prob abilities, and transition distances as a function of the film thickness. De tails of this structure depend on the orientation of the Stark orbitals wit h respect to the film and can be related to the dependence of transition ma trix elements on the active electron's wave vector component parallel to th e surface for the case of a semi-infinite metal. The large variation of the calculated transition distances with the film thickness may result in obse rvable effects in atomic interactions with thin films.