Polarization-dependent optical properties of orthorhombic sulfur in the ultraviolet

Abstract

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 $n$, $k$, ${\ensuremath{\epsilon}}_{1}$, ${\ensuremath{\epsilon}}_{2}$, $\ensuremath{\alpha}$, ${n}_{\mathrm{eff}}$ for the polarizations $\stackrel{\ensuremath{\rightarrow}}{E}\ensuremath{\parallel}\stackrel{\ensuremath{\rightarrow}}{\mathrm{a}}$ and $\stackrel{\ensuremath{\rightarrow}}{E}\ensuremath{\parallel}\stackrel{\ensuremath{\rightarrow}}{\mathrm{b}}$ 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 ${\mathrm{S}}_{8}$ molecule. Exciton creation processes dominate the observed absorption spectra.