Kramers - Kronig analysis of reflectance data: III. Approximations, with reference to sodium iodide

A discussion is given of an approximation used to compute optical and dielectric parameters from normal-incidence reflectance spectra via a Kramers-Kronig dispersion relation. As an example of its usefulness, the reflectance data of single crystal sodium iodide are analysed under different conditions, and the resultant 2 (ω) spectra compared. The errors introduced by the computational technique are less than the probable uncertainty associated with the original experimental data.