MEASUREMENT OF SOME MOLECULAR VIBRATIONAL-ROTATIONAL PARAMETERS WITH AN INFRARED HETERODYNING TECHNIQUE

Abstract

Frequency mixing of three simultaneously oscillating P‐branch laser transitions can be used to obtain accurate spectroscopic information on some of the molecular rotational‐vibrational parameters. This has been demonstrated for the 10‐μ laser transitions of CO₂ and N₂O. The present accuracy is limited by the Doppler widths of the infrared molecular transitions. Improved accuracy is possible to within a small fraction of the Doppler width. Furthermore, it is shown that at elevated pressures where pressure broadening is comparable to or exceeds the Doppler width, mode coupling occurs and the laser tends to oscillate on a single axial mode.