Knowledge Bank

Reliable infrared reflectance data of LiF have been obtained at various temperatures and processed by an Improved Kramers-Kronig dispersion analysis technique. A careful analysis of the imaginary dielectric index ($ϵ$) spectra has provided important insights into the question of electrical and mechanical anharmonicity in the lattice modes of LiF. To further investigate this problem, work has been done on the IR transmission spectra of LiF thin films at high pressures. The optical indices as a function of pressure have been obtained through a Kramers-Kronig transmission dispersion analysis of the transmission values. Results will be presented and evaluated in terms of various models of anharmonicity. The proper methodology to obtain reliable high pressure IR transmission data of LiF thin films will also be outlined.