Temperature dependence of the absorption spectra of nitrogen oxide, nitrogen dioxide and sulfur dioxide in the application of differential optical absorption spectroscopy

Abstract

An experimental set-up has been designed for measurements of differential absorption cross-sections of gases at different temperatures. Preliminary measurements on NO, NO₂ and SO₂ have been carried out at temperatures between 20 and 400 °C by using spectral resolutions in the range 0.26–0.95 nm. These measurements show that the differential absorption cross-sections for all three gases decrease continuously with increasing temperature. Large relative errors resulted when differential absorption cross-sections obtained at room temperature were used in the differential optical absorbtion spectroscopic technique for evaluation of the concentration of gases at high temperatures. The relative errors were of the order of 70% for SO₂ and NO₂ and of the order of 20% for NO at 400 °C.