The shapes of the extreme wings of self-broadened CO<sub>2</sub>(lines have been investigated)in three spectral regions near 7000, 3800, and 2400 cm<sup>-1</sup>. Absorption measurements have been made on the high-wavenumber sides of band heads where much of the absorption by samples at a few atm is due to the extreme wings of strong lines whose centers occur below the band heads. New information has been obtained about the shapes of self-broadened CO<sub>2</sub> lines as well as CO<sub>2</sub> lines broadened by N<sub>2</sub>, O<sub>2</sub>, Ar, He, and H<sub>2</sub>. Beyond a few cm<sup>-1</sup> from the line centers, all of the lines absorb less than Lorentz-shaped lines having the same half-widths. The deviation from the Lorentz shape decreases with increasing wavenumber, from one of the three spectral regions to the next. The absorption by the wings of H<sub>2</sub>- and He-broadened lines is particularly low, and the absorption decreases with increasing temperature at a rate faster than predicted by existing theories.
DARRELL E. BURCH, DAVID A. GRYVNAK, RICHARD R. PATTY, and CHARLOTTE E. BARTKY, "Absorption of Infrared Radiant Energy by CO2 and H2O. IV. Shapes of Collision-Broadened CO2 Lines," J. Opt. Soc. Am. 59, 267-278 (1969)