Atom-atom potential in rotational line broadening for molecular gases: Application to CO lines broadened by CO,N2, O2 and NO

Linewidths in CO-CO, CO-N₂, CO-C₂ and CO-NO collisions have been calculated using an improved potential for atom-atom interactions in addition to the first-order terms of the electrostatic interaction. The energy parameters characterizing the Lennard-Jones potential have been estimated previously from second virial coefficients. Overall agreement between calculated and experimental linewidths (particularly for CO-O₂ mixtures for which the electrostatic contributions are weak) is thus obtained without any adjustable parameters. It is concluded that the atom-atom potential describes the angular dependence of the short-range forces in molecular collisions fairly adequately.