The 10 m region of thioformaldehyde (H2CS) has been recorded at high resolution (0.005 cm-1) using a Fourier transform spectrometer. H2CS was produced by low pressure pyrolysis of a gas flow of C3H5SCH3 in Ar at 560oC or CH3SCl at 1150o C which was introduced into a multipass White cell with an optical path length of 32 m. Forty scans were recorded for the range 750-1400 cm-1 at a total pressure of 0.15 mbar. A thorough analysis of the three lowest frequency fundamental bands, ?3, ?4 and ?6, which fall in this region, has been carried out using a Hamiltonian model which takes explicitly into account the numerous resonances affecting the ro-vibrational energy levels; especially the massive A-type Coriolis resonance between the out-of-plane wagging mode,?4 and the in-plane rocking mode, ?6. These two modes are only separated by 0.83 cm-1, and they are thoroughly mixed. From the fittings, the following band centers were derived: ?o (?4) = 990.18213(40) cm-1, ?o (?6) = 991.02021(50) cm-1 and ?o (?3) = 1059.20476 (30) cm-1 where the uncertainties are one standard deviation. In addition a number of relative line intensities were measured permitting the determination of relative values of the first-order transition moments and therefore relative band intensities for all three bands. Finally a comprehensive list of line frequencies and relative intensities has been generated.
Citation: Journal of Chemical Physics
Pub Type: Journals
High Resolution Infrared Spectrum, line position and intensities, Thiopental, very strong Coriolis resonance