Essentially monochromatic radiation with a frequency corresponding to the frequency of the line center of the P(20) line of the 961-cm-1 CO2 band was obtained from a CO2laser. Using this radiant energy, transmittances of CO2 samples were measured as various broadening gases were added. Self-broadening coefficients of CO2 relative to nitrogen, hydrogen, helium, and argon were determined from the measurements characterizing the transmittance only at the line center; from these measurements ratios of optical collision diameters are calculated.
R. R. Patty, E. R. Manring, and J. A. Gardner, "Determination of Self-Broadening Coefficients of CO, Using CO2 Laser Radiation at 10.6 µ," Appl. Opt. 7, 2241-2245 (1968)