PHOTOACOUSTIC FOURIER-TRANSFORM INFRARED-SPECTROSCOPY OF GASES - A NONEQUILIBRIUM APPROACH

The first order approximations of the nonequilibrium mass balance and momentum balance equations allow predictions of the nonequilibrium temperature-pressure relationships in a photoacoustic effect. This is achieved by setting appropriate boundary conditions for the case when frequency of the normal vibrational modes in infrared is significantly greater than the photoacoustic modulation frequency. Based on the internal energy balance equations, the temperature distributions in the gas phase are derived and tested experimentally, allowing quantitative analysis of the photoacoustic FT-IR spectra.