The vibrational dependence of half-widths of CO2 transitions broadened by N2, O2, air, and CO2

The vibrational dependence of the half-width and line shift for CO2 transitions was investigated using the complex Robert-Bonamy (CRB) formalism. Calculations were made for 24 bands for lower rotational quantum numbers from 0 to 100 for N2-, O2-, air-, and self-collisions with CO2. Starting from the vibrational dependence model proposed by Gamache and Hartmann [Gamache R, Hartmann J-M, J Quant Spectrosc Radiat Transfer 83, 119 (2004)] the percent change in the half-widths is written in terms of the number of vibrational quanta exchanged in the transition raised to a power. The resulting data demonstrate the appropriateness of the model. The measured half-widths are also tested with the model, which demonstrates some of the problems determining the vibrational dependence experimentally. The results show the vibrational dependence of the half-width varies with vibrational band, with the rotational quantum numbers of the transition, and with temperature.

► Vibrational dependence of CO2 half-widths modeled in terms of a quantum coordinate. ► Model works excellently for N2-, O2-, air-, and self-broadening of CO2. ► Number and type of vibrational quanta exchanged determines vibrational dependence. ► Vibrational dependence of half-widths of CO2 is small. ► Vibrational dependence of half-widths depends on J″ and temperature.