COHERENT SATURATION EFFECTS IN A NA2 LASER-INDUCED FLUORESCENCE EXPERIMENT - THEORY AND EXPERIMENT

In this paper we analyse the effect of coherent saturation in the lase r-induced fluorescence (LIF) of molecules. We develop an earlier model introduced by Billy et al. in 1987 of this coherent effect and propos e a simple formula predicting the line shape and the line intensity fo r a laser molecule interaction time considerably longer than the excit ed-state radiative lifetime. The predictions of this formula are teste d on a LIF experiment in which a Na2 molecular beam is excited with a continuous-wave single-frequency dye laser. Considerable spectral broa dening, up to two hundred times the natural linewidth is observed, in good agreement with the model.