Anisotropy of the dielectric constants of trigonal selenium and tellurium between 3 and 30 eV

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Abstract
The reflectivity of Se and Te single crystals has been measured at near normal incidence for photon energies between 3 and 30 eV with the electric field vector lying parallel and perpendicular to the c‐axis of the crystals. The measurements were made using the polarized continuum of the synchrotron radiation of DESY. A Kramers‐Kronig analysis gave the optical constants for both directions of polarization. For both substances electron energy loss measurements are reported. Comparison with optical data gives satisfactory agreement. Even at high energies considerable anisotropic behaviour and several new spectral features are observed. They are discussed in terms of recent band structure calculations.