Direct deduction of the Sellmeier dispersion function from the hook and phase-shift spectrograms

Abstract

A double-layer interferometer is used to produce the hook and the phase-shift interferograms with a tube- and flame-excited D-line of Na atoms. New equations are derived to express the order shift of the perturbed fringes in terms of the coefficients of the Sellmeier dispersion function. A least-squares fit of this function to the experimental data enables its coefficients to be found so that the level population can be more precisely determined than hitherto given. The precision is enhanced at the expense of using a multiray interferometer and a data collection over a relatively wide spectral interval extending from the line core to its far wings.