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

Classical molecular dynamics simulations (CMDS) are used for calculations of the collision-induced absorption (CIA) by pureN₂ 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 aremadeto the CMDS-calculated CIA of pureN₂ 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.