Collision-induced absorption by N₂ near 2.16 µm: Calculations, model, and consequences for atmospheric remote sensing

J. -M. Hartmann (1) , C. Boulet (2) , G. C. Toon

1 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)
2 ISMO - Institut des Sciences Moléculaires d'Orsay

Classical molecular dynamics simulations (CMDS) are used for calculations of the collision-induced absorption (CIA) by pure N₂ in the (2.1-2.2 µm) region of the first overtone band. They lead to reasonable (±15%) agreement with the only two laboratory measurements available, at 97 K and room temperature. Based on these experiment/theory comparisons, empirical corrections are made to the CMDS-calculated CIA of pure N₂ in the 200-300 K temperature range. In addition, the contribution of N₂-O₂ collisions is, in the absence of any laboratory measurement, calculated and a simple semiempirical model (the first of its kind) is built in order to predict the CIA of N₂ under Earth atmosphere conditions. This is successfully validated by comparisons with ground-based atmospheric transmission spectra in the 2.1-2.2 µm region.

Keywords: N<SUB>2</SUB>; collision-induced absorption; 2.16 µm region; atmospheric remote sensing

Domains: Sciences of the Universe [physics]

J. -M. Hartmann, C. Boulet, G. C. Toon. Collision-induced absorption by N₂ near 2.16 µm: Calculations, model, and consequences for atmospheric remote sensing. Journal of Geophysical Research: Atmospheres, 2017, 122, pp.2419-2428. ⟨10.1002/2016JD025677⟩. ⟨insu-03727078⟩