The rotational spectrum of hydrogen sulfide: The H233S and H232S isotopologues revisited

•H233S: accurate measurements (in natural abundance) from 500 GHz up to 1.56 THz.•H232S: rotational spectrum investigated in the THz frequency regime (1.0-1.6 THz).•Lamb-dip technique employed to obtain sub-Doppler resolution.•New parameters: to accurately predict rotational transitions up to 10 THz.

The rotational spectra of two isotopic species of hydrogen sulfide have been revisited. For H233S, which was detected in natural abundance, accurate measurements were performed in the submillimeter-wave region, from 500 GHz up to 1.56 THz, thus allowing improvement of the spectroscopic parameters as well as determination of new high-order centrifugal-distortion constants. The rotational spectrum of the main isotopologue was investigated in the millimeter- and submillimeter-wave region up to 1.6 THz, employing the Lamb-dip technique to obtain sub-Doppler resolution. As a consequence, transition frequencies at 1 THz were retrieved with an accuracy of 1 kHz and the hyperfine structure due to hydrogens was resolved, thus allowing the first determination of the spin-rotation tensor of H in H2S. Improved and new spectroscopic parameters were then provided that allow accurate predictions of rotational transitions up to 20 THz; in particular, the newly determined constants permit prediction of rotational transitions with J < 15, Ka<12 (up to about 10 THz) with expected uncertainties of a few hundreds of kHz.

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