Band-Structure Parameters of Solid and Liquid Xenon

Abstract

Reflection spectra of solid and liquid xenon were obtained in the wavelength range $1200<\mathrm{}\lambda <1600\mathrm{}$ Å. For the solid, the measurements were performed at temperatures between 6 and 160°K. The peak positions of the $\Gamma \left(\frac{3}{2}\right) n=1\mathrm{}$ and $\Gamma \left(\frac{1}{2}\right) n=1\mathrm{}$ intermediate excitons as well as those of the $\Gamma \left(\frac{3}{2}\right) n=2,3\mathrm{}$ Wannier excitons shift to lower energies with increasing temperature throughout the range. A representation of the results as a function of density yields linear plots; the respective points for the liquid also fit well these linear functions. It is inferred that the shifts in the peak positions are caused mainly by the change of energy band edges with thermal expansion, as described by deformation potentials. Application of the effective-mass approximation to the Wannier-exciton peaks yields the temperature (and density) dependence of the band gap, exciton binding energy, and effective mass. In particular, the change $E_{1G}$ of the energy gap between the uppermost valence band and the conduction band with unit dilation is obtained as $E_{1G}=-0.25\mathrm{}$ eV, well within the range of theoretical prediction.