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Updated: May 19, 2026

Characterizing Far-infrared Laser Emissions and the Measurement of Their Frequencies
Published on: December 18, 2015
New infrared bands of nonpolar OCS dimer and experimental frequencies for two intermolecular modes
M Afshari1, M Dehghany, A R W McKellar
1Department of Physics and Astronomy, University of Calgary, 2500 University Drive North West, Calgary, Alberta T2N 1N4, Canada.
Abstract:
Spectra of the nonpolar carbonyl sulfide dimer in the region of the OCS ν(1) fundamental band were observed in a slit-jet supersonic expansion. The jet was probed using radiation from a tunable diode laser employed in a rapid-scan signal averaging mode. Six new bands were observed and analyzed, all of which originate from the dimer ground vibrational state. Three were vibrational fundamentals involving the ((18)OCS)(2) and (16)OCS-(18)OCS isotopologues. They enabled an estimate to be made of the frequency of the infrared-forbidden mode corresponding to in-phase vibration of the OCS monomers in the dimer, a value needed to obtain an intermolecular vibrational frequency from one of the observed combination bands. A relatively weak b-type dimer band centered at 2103.105 cm(-1) was assigned to the OCS 4ν(2) (l = 0) bending overtone. Combination bands were observed involving the geared bend and van der Waals stretch intermolecular modes. The resulting experimental frequencies of 37.5(20) cm(-1) for the bend and 42.9727(1) cm(-1) for the stretch are in good agreement with a recent high level theoretical calculation.
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