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 ${{C}ₛₛ,= 16726±{}30 Hz (spin{-}spin),}{{C}_{{1}₁₀},={-}16239±{}10 Hz (spin{-}rotation{{0ex}{0ex}}constant{{0ex}{0ex}}for {1}₁ rotationalstate),}{{C}_{{1}₀₁},={-}15885±{}10 Hz (spin{-}rotation{{0ex}{0ex}}constant{{0ex}{0ex}}for {1}_{{-}1} rotationalstate).}$ The center frequency of the rotational transition is determined to be ${{ν}}₀=168,762,762,373±{}20$ 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.