Optical Bleaching Kinetics of Ethylene Observed with Pulsed Infrared Laser Excited PhotothermalLens Spectrometry

An overview of the practice of accurate pulsed laser photothermal spectroscopy and the model relating the observed photothermal lens spectroscopy signal to the nonlinear absorption coefficients is given. Details of the assumptions used to derive the vibrational energy state model and the probable excited states involved in the kinetic saturation are discussed. Saturation irradiance and related parameters for ethylene in Ar, He, and N2 buffer gases are given and discussed in light of vibrational relaxation rate constants