Saturation effects in gas-phase photothermal deflection spectrophotometry

This paper describes some effects of optical saturation on a photothermal deflection signal and presents a simple theory to describe these effects. These effects Increase the sensitivity while decreasing the relative error of the method as the Intensity exceeds the saturation Intensity. Detection limits of 1.3 ppbv for chlorodifluoromethane, 2 ppbv for dichlorodifluoromethane, and 3 ppmv for sulfur dioxide, In 13.3 kPa of argon, are found. These detection limits extrapolate to atmospheric detection limits of 170 pptv for chlorodifluoromethane and 260 pptv for dichlorodifluoromethane. The corresponding mass detection limits In the Infrared laser Irradiated volume are 55 fg for chlorodifluoromethane and 70 fg for dichlorodifluoromethane.