Optical Properties of LiF in the Extreme Ultraviolet

Abstract

The reflection spectrum of LiF single crystal was measured in the extreme ultraviolet region at room temperature. The Kramers-Kronig relation was applied to derive the optical constants n and κ from the reflectivity. The maximum absorption coefficient and the peak position of the first fundamental band were determined to be 2.2±0.1×10⁶ cm⁻¹ and 12.7±0.1 ev respectively. Variations of the real and imaginary parts of the complex dielectric constant in the given region were analysed by the quantum-mechanical analogue of the Lorentz dispersion formulas and the oscillator strength of the first fundamental band was determined to be 0.4±0.05/molecule. The value supports the excitation model of the exciton discussed by Dexter on NaCl. Experiments and discussions are also described on the effect of hydrolysis of LiF.