DETERMINATION OF GAS TEMPERATURES AT 295-K-1273-K USING CO VIBRATIONAL-ROTATIONAL ABSORPTION-SPECTRA RECORDED WITH AN FT-IR SPECTROMETER

Fourier transform infrared absorption spectroscopy has been used to determine the rotational temperatures of high-temperature (less-than-or-equal-to 1273 K) CO/N2 gas samples. To achieve this objective, a special gas cell was constructed which permitted the acquisition of absorption spectra of samples containing CO at concentrations of 1-10% by volume in N2 and at temperatures between 295 and 1273 K. The absorption spectra were recorded with the use of a moderate-resolution (0.25 cm-1) FT-IR spectrometer. The rotational temperatures were calculated from the spectra after rigorous correction for photometric errors. Temperatures calculated from the P branch of CO spectra had accuracies of 3.2% or better. In all cases, the calculated temperatures were lower than temperatures recorded with a thermocouple, which had an accuracy of +/- 0.75%. An important factor in the success of these determinations was the adoption of measures to prevent the modulated spectral emission of the hot gases from reaching the detector.