The first high-resolution analysis of the 10-μm absorption of thioformaldehyde

The 10 mu m region of thioformaldehyde (H2CS) has been recorded at high resolution (0.005cm(-1)) using a Fourier transform spectrometer. H2CS was produced by low-pressure pyrolysis of a gas flow of C3H5SCH3 in Ar at 560 degrees C or CH3SCl at 1150 degrees 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 wavenumber fundamental bands, v(3), v(4) and v(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, v(4), and the in-plane rocking mode, v(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: v(o) (v(4)) = 990.18213(40) cm(-1), v(o) (v(6)) = 991.02021(50) cm(-1) and v(o) (v(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 wavenumbers and relative intensities has been generated. (C) 2007 Elsevier Ltd. All rights reserved.