Reflection Spectrum of Solid Argon in the Vacuum Ultraviolet

The reflectance of solid Ar has been measured at 20°K for an angle of incidence of 15° in the photon energy range from 10 to 30 eV using the synchrotron radiation of DESY. The reflectance data reveal a spin-orbit-split exciton series with sharp maxima converging to about 14 eV together with broader peaks above 14 e V due to transitions between the valence and conduction band. The results are compared with the absorption spectrum associated with the $2p$ core levels.