PHOTOACOUSTIC RAMAN-SPECTROSCOPY (PARS) USING CW LASER SOURCES

We have devised a new nonlinear spectroscopic technique, photoacoustic Raman spectroscopy (PARS), which uses acoustic methods to detect energy deposited in a molecular gas by the process of stimulated Raman scattering. The technique was demonstrated by stimulated Raman excitation of the 2916.7-cm -1 ν1 symmetric stretch vibrational mode of CH 4 using two cw laser sources (an argon ion laser at 514.5 nm and a tunable dye laser near 605.4 nm). Excellent agreement between calculated and experimentally observed PARS signals was obtained for CH4.