Heterodyne frequency measurements with a tunable diode laser-CO(2) laser spectrometer: spectroscopic reference requencies in the 9.5-microm band of carbonyl sulfide.

The frequencies of twelve carbonyl sulfide absorption lines near 9.5 microm have been measured by means of a heterodyne frequency measuring technique, which uses a frequency stabilized CO(2) laser and a tunable diode aser. The diode laser was locked to the peak of each OCS absorption line by means of a first derivative frequency lock procedure. In addition to lines in the 02(0)0-00(0)0 band, measurements also include some nearby OCS hot band features as well as lines in isotopically enriched samples of OC(34)S, O(13)CS, and (18)OCS. These measurements are part of an effort to provide frequency standards for the calibration of tunable IR laser devices.