High‐resolution Fourier transform measurement of the NO2 visible and near‐infrared absorption cross sections: Temperature and pressure effects

Abstract

High‐resolution NO2 absorption cross sections have been obtained in the near‐IR (NIR) and visible regions using a Fourier transform spectrometer coupled to a multiple reflection cell. Spectra were recorded at 0.05 cm−1 in the NIR region (10,800–15,100 cm−1) and at 0.1 cm−1 in the visible region (13,800–26,000 cm−1), under various pressure conditions (pure NO2 and NO2/air mixtures) and at three temperatures (220, 240, and 294 K). The effects of the temperature and the pressure on the NO2 cross sections have been investigated. As expected, an increase of temperature results in a decrease of the absorption at the maxima of the absorption bands and an increase at the minima. From the measurements performed with pure NO2 at different temperatures a linear regression of the cross section with temperature has been carried out. This enabled the cross sections to be reproduced within 2% at room temperature and 7% at the lower temperatures. The variation of the cross sections with the total pressure of NO2/air mixtures has also been investigated at high resolution.