3d photoabsorption in gaseous and solid xenon

The 3d absorption spectra of gaseous and solid xenon are compared. The spectrum of the gas agrees substantially with earlier data apart from two additional weak peaks about 1.3 and 5.0 eV above the M 5 threshold. Comparison with the 3 P 1 and 3 D 1 lines in the absorption spectra of Ce 4+ , La 3+ , Ba 2+ and Cs + suggests that the weak xenon peaks represent transitions into resonantly localised continuum f states. No corresponding structure has been reported in the 4d spectrum. The gross structure of the spectrum of the solid is similar to that of the gas with the dominating M 4 and M 5 continuum peaks at the same energies and with similar cross sections. Notable differences are disappearance of the 1.3 eV peak, enhancement of the 5.0 eV peak and the appearance of weak maxima extending from 7.8 eV above the M 5 threshold to higher energy, across both M 4 and M 5 continuum peaks. This structure, which lies above the range of existing density of states calculations, is attributed to scattering from surrounding atoms. No corresponding structure has been reported either in the 4d spectrum of solid xenon or in the isoelectronic M 4,5 spectra of I - , Cs + , Ba 2+ or La 3+ in solids.