The pressure-modulated near-infrared emission spectrum of a gas consists of a set of vibration-rotation bands. The intensity of the emitted radiation is a rapidly varying function of frequency. The transmission of this radiation through various gas samples has been investigated for absorbing atomspheric gases such as carbon dioxide, carbon monoxide, nitrous oxide, and methane; the effects of pressure-broadening of spectral lines by inert gases such as argon and nitrogen have been considered. The transmittance of radiant power has been shown to depend on the composition of the emitting sample and the compression ratio employed as well as on the composition of the absorbing sample. Possible application of pressure-modulation techniques to atmospheric transmission studies is suggested.
RICHARD R. PATTY and DUDLEY WILLIAMS, "Pressure-Modulation Study of the Absorption of Non-Black Thermal Radiation," J. Opt. Soc. Am. 52, 546-550 (1962)