ABSOLUTE MEASUREMENT OF GAS CONCENTRATIONS AND SATURATION BEHAVIOR INPULSED PHOTOACOUSTICS

Absolute photoacoustic measurements of the signal strength yielding th e concentration and absorption coefficient of ethylene were performed in the IR on the weakly and strongly absorbed 10P(10) and 10P(14) line s of a pulsed CO2 laser, respectively, using an optimized cylindrical acoustic resonator with Q similar to 1000. The calculated photoacousti c signal strength agreed with the measured signal within an experiment al error of 10%. With the 157 nm radiation of an F-2 laser pulsed phot oacoustics was extended into the VUV region where photodissociation of C2H4 occurs. Optical saturation phenomena were observed for pulsed CO 2 laser and F-2 laser excitation below 3 mJ pulse energy. (C) 1998 Els evier Science B.V.