Optical Properties of Dilute Solid-Rare-Gas Mixtures in the Extreme Ultraviolet

The absorption spectra of thin films of mixtures of the rare gases Xe, Kr, Ar, and Ne have been measured in the photon range 40 - 260 eV, i.e., in the region of Ne-$2s$, Ar-$2p$, Kr-$3d$, and Xe-$4d$ transitions. In most cases a continuous shifting of the energetic position of the absorption peaks of the pure-rare-gas solids upon addition of another rare gas of of ${\mathrm{N}}_2$ can be observed, thus indicating a dilute mixing of both components over the whole range of concentrations. The shift of the absorption peaks can be understood in terms of the conduction-band density of states of pure-rare-gas solids.