Pressure effects on the spectral line shape of broad-band degenerate four-wave mixing

The spectral line shape of degenerate four-wave mixing signals induced by b road-bandwidth laser fields in nitric oxide in the presence of nitrogen buf fer gas is studied by high-resolution Fabry-Perot interferometry. The spect rum is analysed using a theory, previously developed by Smith and Ewart, wh ich predicts a Voigt-type profile, dependent on the collision rate Gamma, i n which the collisional width is 2 Gamma in the collisionally dominated reg ime and 4 Gamma in the limit of dominant Doppler broadening. The results sh ow a collisional component of 3 Gamma consistent with the intermediate regi me studied at a N-2 pressure of 0-150 Torr. The Doppler component of the me asured line profile, calculated in terms of the theoretical profile, corres ponded to a temperature of 280 +/- 60 K in agreement with the measured room temperature. The decay of the spectrally integrated signal intensity with increasing pressure was found to agree with theoretical prediction.