The shapes of the extreme wings of self-broadened CO2(lines have been investigated)in three spectral regions near 7000, 3800, and 2400 cm-1. 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 CO2 lines as well as CO2 lines broadened by N2, O2, Ar, He, and H2. Beyond a few cm-1 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 H2- and He-broadened lines is particularly low, and the absorption decreases with increasing temperature at a rate faster than predicted by existing theories.
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A study has been made of the absorption due to individual lines and Q branches of CO2 bands in the 15-to 18-µ spectral region. The strengths and widths of absorption lines on the low-frequency side of the v2 fundamental band and in the 02°0–0110 band of C12O162 have been measured. In the latter band the variation of line strength and width with J has been determined as well as the Coriolis interaction parameter. The strengths of five other bands of C12O162 have been determined from measurements on their Q branches, and the strengths of the v2 fundamental bands of the isotopes C13O162 and O18C12O16 have been estimated. The rotational structure of the v2 fundamental Q branch for C12O162 is partially resolved, and the band constants determined. The v2 fundamental band head of the O18C12O16 isotope is reported.The spectra were taken in 1956 after construction of the large infrared spectrometer at the Laboratory of Astrophysics and Physical Meteorology, The Johns Hopkins University. This f/6 spectrometer utilizes 3-in. long curved slits and a 14- by 12-in. grating in a Fastie-Ebert mounting. It is demonstrated that this instrument has available an optical slit width of 0.06 cm-1 at 17 µ.
