Interpretation of the Ultraviolet Spectrum of Trigonal Selenium

Based on an earlier pseudopotential calculation [1] the imaginary part of the dielectric function for Se is recalculated between 6 and 11 eV including lifetime broadening. Our results agree well with UV reflectivity measurements by Leiga [3], a detailed interpretation of which is given. In particular, the strong polarization dependence of several peaks is explained, and also the crossover of the ∥ and ⟂ spectra at 10 eV. The spectrum is shown to be largely determined by additional gaps between the subbands of both the valence band and the conduction band.