Resonance Raman scattering of light from a diatomic molecule

Resonance Raman scattering from a homonuclear diatomic molecule is considered in detail. For convenience, the scattering may be classified into three excitation frequency regions—off-resonance Raman scattering for incident energies well away from resonance with any allowed transitions, discrete resonance Raman scattering for excitation near or in resonance with discrete transitions, and continuum resonance Raman scattering for excitation resonant with continuum transitions, e.g., excitation above a dissociation limit or into a repulsive electronic state. It is shown that the many differences in scattering properties in these three excitation frequency regions may be accounted for by expressions derived from simple perturbation theory. Scattering experiments from molecular iodine are presented which test and verify the general scattering theories. Spectral measurements, time decay measurements, and pressure broadening measurements were made on I2 in the discrete resonance Raman scattering region; and spectral measurements at several excitation frequencies were made in the continuum resonance Raman scattering region. In each case calculations based on general theories correctly describe the experimental data.