OBSERVATION OF VIBRATIONAL ENHANCEMENT USING PRE-RESONANT INFRARED 4-WAVE-MIXING

A vibrational enhancement of the third order optical susceptibility (c hi((3))) is found for the C-H stretch of hexane using nonparametric in frared four wave mixing. Two tunable infrared beams and one visible la ser were focused into hexane with deuterobenzene as an internal standa rd. The four wave mixing enhancement was measured for different freque ncies in the preresonant region using the interference between a coher ent Raman process in the deuterobenzene and the vibrationally enhanced nonparametric process from the hexane. The frequency dependence of th e nonparametric process matches that expected for vibrational enhancem ent. (C) 1997 Elsevier Science B.V.