High-resolution study of anomalous dispersion in the ruby R lines

The real and imaginary parts of the complex index of refraction in the R-line region of ruby have been measured near liquid-nitrogen temperature with sufficient resolution that the R-line doublet structure was well resolved. A modification of the usual Babinet compensator technique was used for the refractive-index measurements, which were found to correlate with the absorption measurements as predicted by the Kramers-Kronig relations. An attempt at direct quantitative verification of the dispersion relations for an optically pumped sample is also described.