ISSN:
1432-0649
Keywords:
33.20.Kf
;
34.50.Ez
;
82.20.Rp
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract We describe the effects of He, Ar and N2 on the resonant degenerate four-wave-mixing spectrum of NO2. We report results obtained using the phase-conjugate and forward-geometry experimental configurations for various laser intensities and bandwidths. We find that the effect of buffer-gas pressure on the reflectivity of the laser-induced grating depends critically on the relative value of the laser intensityI to the saturation parameterI sat. WhenI ≈I sat the four-wave-mixing signal initially decreases with increasing buffer-gas pressure. However, at pressures above ca. 100 Torr the signal increases. WhenI ≪I sat the signal is found to increase with buffer-gas pressure even at the lowest pressures studied. These observations do not agree with the standard model of degenerate four-wave mixing in the gas phase. We have investigated the source of these effects by employing different polarisation geometries of the pump and probe laser fields, and conclude that thermal gratings are responsible for the increase in signal observed at high buffer-gas pressure. This conclusion is supported by a simple gas kinetic model.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01082067
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