X-ray-edge problem in metals. II. Alkali-metal atoms adsorbed on alkali and other metal surfaces

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Abstract
Outer-core spectra are reported for Cs and Rb adsorbed on clean surfaces of the alkali metals and Mg. In most cases the spectrum at threshold resembles a broadened resonance line close to the energy of the atomic transition, with additional structure on the high-energy side. With increasing electron density of the substrate, the line broadens and disappears into a profile which increases approximately linearly from zero at a red-shifted threshold. In no case does the adsorbate spectrum resemble the sharp edge and overshoot observed for the bulk metal. Above about one monolayer in many cases, a discrete feature occurs on the red wing of the threshold line and grows systematically with coverage into the dominant spectrum of the pure bulk adsorbate at about 5 monolayers. The general behavior is qualitatively consistent with the behavior of alkali-alkali alloys, reported in the paper which immediately precedes this one.