Frequency-angular diffusion of intense quasiresonant radiation

The probing field method is used to demonstrate experimentally that the frequency-angular diffusion of intense quasi-resonant radiation derives from the four-photon resonant parametric scattering of light under conditions of large amplification in a narrow channel of one of the scattering components. A pulsed dye laser whose frequency is tuned near the frequency (omega sub 3/2) of the resonant transition 3Sl/2-3P3/2 in NaI is used in the experiment. The characteristic frequency-angular scattering diagram is included. Bichromatic dye laser radiation is used in the experiments with the probe field.