NO2 absorption cross section and its temperature dependence

Abstract

Presented in this text is a compilation of existing absorption cross sections of NO2, mainly at room temperature but also at lower and higher temperatures, with a quantitative comparison of their cross sections and wavelength calibrations. From this, we concatenate three selected cross sections (slightly corrected) in order to cover the widest possible spectral range from 300 to 708 nm, at a resolution of 0.05 nm. At longer wavelengths, λ>708 nm, the (much weaker) cross section exists only at low‐resolution (≅1 nm), giving a low‐resolution cross section from 300 to 908 nm. We show that the cross‐section temperature dependence (data exist from 200 to 673 K) can be decomposed into two parts, a bell‐shaped envelope and superimposed spectral fluctuations. The envelope broaden slightly with increasing temperature, while the amplitude of the fluctuations decreases (increases) with increasing (decreasing) temperature. Finally, we sketch the “reflection” model, which allows us to get the cross‐section envelope from the shapes of the ground state vibrational wave function and of the potential energy surface of the first excited state.