Sub-Doppler Frequency Measurements on OCS at 87 THz (3.4 μm) with the CO Overtone Laser

Abstract

Sub-Doppler frequency measurements have been made on three transitions of OCS in the 87-THz region (near 2900 cm−1). The CO overtone laser was used as the saturating laser. Polarization spectroscopic techniques utilizing optical heterodyne detection were used to observe the features and subsequently provide the discriminant for locking the overtone laser to the OCS transitions. A CO2 laser synthesizer was used to measure the frequency of the CO overtone laser and thereby measure the frequencies of the OCS lines. The resulting frequencies of the three new measurements are: 1001-0000 P(27), 87 117 278.496(50) MHz; 111ƒ1-011ƒ0 R(14), 87 222 001.143(70) MHz for OCS; and for the OC34S 1001-0000 P(9), 87 010 586.667(75) MHz, where the numbers in parentheses are the uncertainties in the last digits. These new numbers have been fitted along with more than 5700 other data points in our OCS data bank and improved constants have been obtained. These latest constants are used to calculate updated calibration tables containing values with much smaller uncertainties; three such tables are included.