Fluorescence, absorption and scattering of light in ruby

Abstract

The paper deals with the results of a spectroscopic investigation of the fluorescence, absorption and scattering of light in ruby. The first order lattice spectrum of alumina is shown to possess eighteen normal modes of vibrations. Two Raman lines having frequency shifts of 376 and 412 cm^-1 have been obtained with a single crystal of alumina. The fluorescence and absorption spectra of ruby have been recorded using specially sensitized infra-red plates to register the bands in the long wavelength region with good intensity. The polarisation characters of the bands have also been studied with reference to the direction of the optic axis of the crystal and the direction of polarisation of the incident beam. From a perusal of the results, the emission bands have been divided into two groups viz., (1) electronic bands caused by transitions of the shielded electrons of Cr⁺⁺⁺ ion, (2) vibrational bands arising from a modulation of the electronic transitions by the crystal lattice vibrations. The frequency shifts of eight of the vibrational bands from the principal doublets agree fairly well with one or the other of the observed Raman and infra-red frequencies of alumina. The polarisation characters of the bands on the Stokes sides are also in good agreement with those of the corresponding bands on the anti-Stokes side.