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

The magnetic hyperfine structure of the $1_{-1\mathrm{}}\leftrightarrow 1_1$ rotational transition of ${\mathrm{H}}_2$S has been fully resolved in a millimeter electric-resonance spectrometer. The hyperfine components have been measured with an accuracy of 2 parts in ${10}^{10}$. The hyperfine coupling constants are determined to be $\{{\mathrm{C}}_{\mathrm{ss}},= 16726\pm 30 \mathrm{Hz} (\mathrm{s}\mathrm{p}\mathrm{i}\mathrm{n}-\mathrm{s}\mathrm{p}\mathrm{i}\mathrm{n}),\}\{{\mathrm{C}}_{1_{10}},=-16\mathrm{}239\pm 10 \mathrm{Hz} (\mathrm{s}\mathrm{p}\mathrm{i}\mathrm{n}-\mathrm{r}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{c}\mathrm{o}\mathrm{n}\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{n}\mathrm{t}\mathrm{f}\mathrm{o}\mathrm{r} 1_1 \mathrm{rotational}\mathrm{state}),\}\{{\mathrm{C}}_{1_{01}},=-15\mathrm{}885\pm 10 \mathrm{Hz} (\mathrm{s}\mathrm{p}\mathrm{i}\mathrm{n}-\mathrm{r}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{c}\mathrm{o}\mathrm{n}\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{n}\mathrm{t}\mathrm{f}\mathrm{o}\mathrm{r} 1_{-1\mathrm{}} \mathrm{rotational}\mathrm{state}).\mathrm{}\}$ The center frequency of the rotational transition is determined to be ${\nu }_0=168,762,762,373\mathrm{}\pm 20$ 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 $4_0\leftrightarrow 4_2$ rotational transition of ${\mathrm{H}}_2$S.