Radiative Measurements of Pressure Modulator Operation

Abstract

The pressure modulator is extensively used in atmospheric measurements but is not well characterized in terms of its spectroscopic operation. A series of measurements on a carbon monoxide radiometer is described and comparisons are made with theoretical calculations for the same conditions. Agreement is found between theory and experiment for normalized cell transmissions. Diode laser spectroscopic measurements are also found to give satisfactory agreement if there is some temperature cycling in the modulator cell. Some variation is found in the absolute measurements of equivalent width. The possible reasons for this discrepancy are discussed.