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.