Hans J. Liebe

Abstract:

The O₂-spectrum of dry air was studied with a resonance spectrometer under controlled laboratory conditions. Key parts of the instrumentation were an automatic network analyzer and a one-port Fabry-Pérot resonator affording an effective path length of 240 m. Measurements were made at frequencies between 49.3 and 67.2 GHz in 0.1 GHz increments for eleven pressure steps (1–100 kPa) and three different temperatures (7-30- 53°C). More than 5 10⁶ data points (SI parameters) have been recorded and reduced to about 5,000 absorption values α (dB/km). Measurement uncertainties were estimated to be typically the worse of ±0.05 dB/km or 2 percent. The collective spectral behavior of 38 pressure-broadened O₂ lines is described by the model MPM (NTIA Report 91-272, March 1991). A comparison of the absorption results with MPM predictions reveals systematic differences which correlate with O₂ line width and overlap parameters. An interpretation of the extensive data set with Rosenkranz's overlap theory [JQSRT 39(4), 287–297, 1988] is underway.

Keywords: O2-spectrum

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