Electron resonances in alkali-metal overlayers on metals

Based on a jellium model using a self-consistent potential modified to an image-potential shape outside the surface of Na and Cs monolayers on Al(111), we have identified resonances in the overlayer-induced density of electron states. This jellium-model description of the electronic structure is supported by the good agreement between the calculated energy for the lowest unoccupied level and the observed energy by inverse photoemission for (2×{}2)Na on Al(111).