DEGENERATE 4-WAVE-MIXING WITH A TUNABLE EXCIMER-LASER

We use a simple, forward-geometry degenerate four-wave mixing setup to monitor weak absorptions of various gas-phase molecules with a tunabl e excimer laser. With this technique, state-selective detection of H-2 , CO, H2O, and O2 is demonstrated. The dependence of the forward-geome try degenerate four-wave mixing signals on various experimental parame ters (e.g., pressure, laser power) is determined. Several mechanisms f or the generation of the observed signals are discussed, including dif fraction from density gratings or thermal gratings and two-photon dege nerate four-wave mixing.