Four-wave mixing stimulated emission

Vaccaro P H 1995 Resonant four-wave mixing spectroscopy a new probe for vibrationally-excited species Molecular Dynamics and Spectroscopy by Stimulated Emission Pumping (Advances in Chemistry Series) vol 7, ed H-L Dai and R W Field (Singapore World Scientific) p 1... 

In passing, we note that parametric four-wave mixing processes could in principle contribute to the effects described above. Thus, in the single-beam case, the CARS process co + co cOi + CO2 single center could also result in the synergistic excitation of two chemically different centers. Equally in the double-beam case, the four-wave interaction coi +o 2-> (o + (o followed by absorption of the frequency co, could contribute to the excitation of a pair of neighboring molecules of the same species. However, both of these four-wave interactions will be relatively ineffectual unless (one of) the emission frequencies is stimulated by an additional source moreover, the processes described here are not associated with the wave-vector matching characteristics of CARS and related phenomena. 

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