Optical Constants and Electronic Structure of Crystalline and Amorphous As2S3 in the 3 to 35 eV Range

By Kramers‐Kronig analysis, the complex dielectric constant tensor of monocrystalline As2S3 is deduced from energy losses in the 3 to 35 eV range suffered by a 40 keV electron beam. The weak optical anisotropy observed in this spectral range is explained and the results are discussed in terms of a valence bonding model with two groups of valence bands. Upon the amorphous to crystalline transition it is the optical transitions originating in the resonance bonds which are only influenced.