Quantitative discrimination of gas-phase species based on single-wavelength nonlinear intensity dependent pulsed infrared laser excited photothermal deflection signals

A sensitive photothermal deflection spectroscopy experlment is described whlch allows for sknultaneous collection of pulsed infrared excltatlon laser energy and slgnal data. Processing of these data for elucldatlon of nonllnear excltatlon laser energy dependent absorption effects Is Illustrated for 1,3-butadiene, chlorodlfluoromethane, and dlchlorodtfluoromethane. Both multiphoton and saturation absorptlon behavior are observed for the halocarbons. Thls nonlinear excltatlon energy dependent absorption behavlor Is emplrlcally modeled by a power serles uslng llnear regression. The resultlng power serles are used to analyze mlxtures of the two halocarbon species. It Is found that slngle-wavelength dlscrlminatlon and quantltatlon of these species can be performed with analyte levels below 10 ppm (v/v) In argon.