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

TLDR

The study investigates how temperature and pressure affect NO₂ absorption cross sections. High‑resolution NO₂ absorption cross sections were measured with a Fourier‑transform spectrometer and multiple‑reflection cell across 10,800–26,000 cm⁻¹ at 0.05–0.1 cm⁻¹ resolution, varying temperature (220–294 K) and pressure (pure NO₂ and NO₂/air mixtures), and cross‑section temperature dependence was modeled by linear regression. Increasing temperature reduces absorption at band maxima and increases it at minima, and the temperature‑dependent cross sections can be reproduced within 2 % at room temperature and 7 % at lower temperatures.

Abstract

High‐resolution NO 2 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 NO 2 and NO 2 /air mixtures) and at three temperatures (220, 240, and 294 K). The effects of the temperature and the pressure on the NO 2 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 NO 2 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 NO 2 /air mixtures has also been investigated at high resolution.