Infrared collision-induced absorption by N₂near 4.3 μm for atmospheric applications: Measurements and empirical modeling

Accurate measurements of collision-induced absorption by pure nitrogen in the fundamental band near 4.3 μm have been made in the 0–10 atm and 230–300 K pressure and temperature ranges, respectively. A Fourier-transform spectrometer was used with a resolution of 0.5 cm^-1. The current measurements, which agree well with previous ones but are more precise, reveal that weak features are superimposed on the broad N₂continuum. These features have negligible temperature dependence, and their origin is not clear at the present time. Available experimental data in the 190–300 K temperature range have been used to build a simple empirical model that is suitable for use to compute atmosphericN₂absorption. Tests indicate that this model is accurate unlike the estimates produced by widely used atmospheric transmission codes.