Laboratory Measurements Of The Infrared Absorption By H2O And CO2 In Regions Of Weak Absorption

Laboratory measurements of the infrared absorption by CO2 and H2O in regions of weak absorption has provided new information on the shapes of the extreme wings of the absorption lines. CO2 lines absorb much less in the wings than Lorentz-shaped lines with the same intensities and half-widths; N2-broadened lines absorb even less than self-broadened lines. Both self-broadened and N2-broadened H2O lines appear to absorb more over a large portion of the wings than Lorentz-shaped lines. Like CO2 lines, the wings of self-broadened H2O lines absorb much more than the N2-broadened H2O lines. Absorption by the wings of all of the lines decreases unpredictably fast with increasing temperature. Much of the H2O absorption frequently attributed to dimers may be due to the extreme wings of self-broadened H2O lines.