Microwave spectrum and molecular structure of the HSC radical

Abstract

The HSC radical, that is a geometrical isomer of the HCS radical, has been identified and characterized by microwave spectroscopy. The HSC radical has been produced in a discharge plasma of a gaseous mixture of H2S and CO, and its rotational spectral lines are observed with a source-modulation spectrometer and a Fourier-transform millimeter-wave spectrometer. The spectrum of the deuterated species, DSC, has also been measured with a source-modulation spectrometer. Rotational constants, centrifugal distortion constants, and spin–rotation interaction constants with their centrifugal distortion corrections for HSC and DSC are determined from the observed transition frequencies by a least-squares method. Furthermore hyperfine interaction constants of the hydrogen nucleus are also determined for HSC. The Fermi contact term of the hydrogen nucleus takes a large positive value, 288.845±0.185 MHz, which indicates that the HSC radical is a σ radical (2A′) in the ground electronic state. The harmonic force field is evaluated from the obtained centrifugal distortion constants and inertial defects. The zero-point vibrational average structure is determined as follows; rz(H–S)=1.390±0.003 Å, rz(S–C)=1.6403±0.0005 Å and αz(HSC)=104.2±0.2°.