The uv absorption spectra of adsorbed Xe and CO in LiF films were investigated. The3P1thinsp;larr;thinsp;1S0and1P1thinsp;larr;thinsp;1S0transitions of Xe were observed. These atomic absorption lines are very much broadened (1000ndash;200 cmminus;1) in the adsorbed state. The bands are shifted relative to the gas phase and the magnitude of the shift is a function of the surface coverage. The shift ranges from several hundred wavenumber units to the blue for low coverages to several hundred wavenumber units to the red for high coverages. Removal of orbital degeneracy, if present, is smaller than the bandwidth. TheA1Pgr;thinsp;larr;thinsp;X1Sgr;plus;transition of adsorbed CO was investigated in the wavelength region 1600ndash;1300 Aring;. The bands are quite narrow compared to the bands of adsorbed Xe. Each vibronic state is split into two components. The magnitude of the splitting is 600ndash;1000 cmminus;1. This splitting is believed to be due to the removal of thepgr;hyphen;orbital degeneracy by the LiF surface field.
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