The spectral line shape of degenerate four-wave mixing signals induced by broad-bandwidth laser fields in nitric oxide in the presence of nitrogen buffer gas is studied by high-resolution Fabry-Perot interferometry. The spectrum is analysed using a theory, previously developed by Smith and Ewart, which predicts a Voigt-type profile, dependent on the collision rate Gamma, in which the collisional width is 2 Gamma in the collisionally dominated regime and 4 Gamma in the limit of dominant Doppler broadening. The results show a collisional component of 3 Gamma consistent with the intermediate regime studied at a N-2 pressure of 0-150 Torr. The Doppler component of the measured line profile, calculated in terms of the theoretical profile, corresponded 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. [References: 19]
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