Anisotropy in the reflectivity and band structure of monoclinic selenium

Abstract
The molecular crystal α-monoclinic selenium has been found to be inadequately described by previous calculations of molecular eigenvalues. A simple band model for monoclinic selenium is proposed on the basis of a new determination of the eigenvalues for the Se8 ring molecule and consideration of the intermolecular interactions arising from the symmetry of the crystal structure. The model is supported by near-normal incidence polarization-dependent reflectivity measurements at room temperature and 77 K over the energy range 1.5–4.5 eV. This interpretation is further supported by a Lorentzian analysis of the data.