Hyperfine Structure in the Millimeter Spectrum of Hydrogen Sulfide: Electric Resonance Spectroscopy on Asymmetric-Top Molecules

The magnetic hyperfine structure of the 1_-1<-->1₁ rotational transition of H₂S has been fully resolved in a millimeter electric-resonance spectrometer. The hyperfine components have been measured with an accuracy of 2 parts in 10¹⁰. The hyperfine coupling constants are determined to be C_ss= 16 726+/-30 Hz (spin-spin),C₁₁₀=-16 239+/-10 Hz (spin-rotation constant for 1₁ rotational state),C₁₀₁=-15 885+/-10 Hz (spin-rotation constant for 1_-1 rotational state). The center frequency of the rotational transition is determined to be ν₀=168,762,762,373+/-20 Hz. Several sources of frequency shift and line distortion have been investigated. Seven rotational transitions of hydrogen sulfide have been observed, four of them in the electric-resonance spectrometer. The electric-resonance technique has been extended to a wavelength of 813 μ by observation of the 4₀<-->4₂ rotational transition of H₂S.