Collisional redistribution of fluorescence radiation

Abstract We derive a general quantum-mechanical expression for the spectral distribution of resonance fluorescence of an atom in a perturber gas, excited by a monochromatic polarized non-saturating light source. The Doppler effect is included and we avoid the restrictions of the impact limit. We specialize the equations to the simple case of non-degenerate states in order to obtain an expression for the redistribution function in terms of the ordinary line profile as measured in absorption and of the corresponding dispersion function. We study the case of far-wing excitation and we show that the results match the experimental observations reported by Carlsten and Szoke.