Absorption of the 4- to 6-millimeter wavelength band in the atmosphere

The analysis of an extensive series of zenith attenuation measurements of the atmosphere on both sides of the oxygen absorption spectrum (48–72 GHz) elucidates the absorption characteristics of the 4- to 6-mm wavelength band. With the sun as a source, zenith attenuation measurements were made and used as a function of the precipitable water content of the atmosphere to determine the zenith attenuation coefficients of precipitable water. From these coefficients and measurements of the total precipitable water in the atmosphere the oxygen components of the zenith attenuations were determined. The zenith oxygen attenuations as a function of frequency and altitude are used to compare the theories for collision-broadened spectral lines and to develop a new expression for pressure-broadened spectral lines. The Gross and the Lorentz theories and the newly derived two-piece linear expression for collision-broadened spectral lines of atmospheric oxygen provide a theoretical fit to the measured data of 8.3%; the Van Vleck-Weisskopf theory for the shape of collision-broadened lines provides a fit of 13.8%.