Effect of collision narrowing on atmospheric transmittance.

The effect of collision narrowing on inhomogeneous, long-path atmospheric transmittance is discussed. The different temperature and pressure dependence of the collision narrowing and the collision broadening contributions to the absorption line shape can result in a significant change in calculated values of both the absolute and relative transmitted intensity. Illustrative calculations are presented for a narrow-band source that is resonant with selected absorption lines of CO(2) and is transmitted along a variety of atmospheric paths.