OBSERVATION OF SATURATION DIP IN DEGENERATE 4-WAVE-MIXING AND 2-COLORRESONANT 4-WAVE-MIXING SPECTRA OF JET-COOLED CH

we report both degenerate four-wave mixing (DFWM) and two-color resona nt four-wave mixing (TC-RFWM) spectra of jet-cooled CH produced from p hotolysis of CHBr3 at 248 nm. A vibrational temperature 3400 +/- 200 K is determined for CH, in agreement with measurements of laser-induced fluorescence. Line splitting with a dip at the center due to saturati on is observed at total laser energies greater than 100 mu J in both D FWM and TC-RFWM; it is more readily observed with the all-parallel YYY Y polarization scheme than in other polarization arrangements. Possibl e models for the saturation dip are discussed. (C) 1998 Elsevier Scien ce B.V. All rights reserved.