Vacuum ultraviolet properties of beryllium fluoride glass

Abstract

The reflectivity of pure and multicomponent BeF2 glasses has been measured in the spectral range 8-50 eV. Optical transmission and ultraviolet photoelectron spectroscopy are also described. The data are interpreted to indicate that pure BeF2 glass has a 13.8-eV band gap and an exciton peak at 12.8 eV. An alternative interpretation of the spectra in terms of a direct-forbidden band edge analogous to SiO2 would suggest a smaller band gap. BeF2 should ultimately be capable of an ultraviolet transmission range comparable to that of LiF, though extrinsic factors now limit the transparency range.