Polarization-dependent optical properties of orthorhombic sulfur in the ultraviolet

The optical anisotropy of the ultraviolet absorption of orthorhombic sulfur has been investigated by means of polarization-dependent reflectivity measurements to 14 eV. Optical response functions n, k, ε₁, ε₂, α, neff for the polarizations →E∥→a and →E∥→b have been derived from the reflectivity spectra by means of Kramers-Kronig analysis. The observed electronic transition energies, notably the lowest allowed transitions near 4 eV and the strong transitions near 9.5 eV, are interpreted on the basis of a recent calculation of the electronic structure of the S₈ molecule. Exciton creation processes dominate the observed absorption spectra.