Gas phase detection and rotational spectroscopy of ethynethiol, HCCSH

• Published in: Molecular physics Vol. 117; no. 9-12; pp. 1381 - 1391
• Main Authors: Lee, Kin Long Kelvin, Martin-Drumel, Marie-Aline, Lattanzi, Valerio, McGuire, Brett A., Caselli, Paola, McCarthy, Michael C.
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 18-06-2019; Taylor & Francis Ltd
• Subjects: astrochemistry; Chemical Physics; Exothermic reactions; Fourier transforms; Millimeter waves; Molecular structure; Nozzles; Physics; quantum chemistry; Radio frequency discharge; Recombination reactions; Rotational spectra; Rotational spectroscopy; Substitution reactions; Terahertz frequencies; Vapor phases
• ISSN: 0026-8976; 1362-3028
• DOI: 10.1080/00268976.2018.1552028

We report the gas-phase detection and spectroscopic characterisation of ethynethiol (
), a metastable isomer of thioketene (
) using a combination of Fourier-transform microwave and submillimetre-wave spectroscopies. Several a-type transitions of the normal species were initially detected below 40 GHz using a supersonic expansion-electrical discharge source, and subsequent measurement of higher-frequency, b-type lines using double resonance provided accurate predictions in the submillimetre region. With these, searches using a millimetre-wave absorption spectrometer equipped with a radio frequency discharge source were conducted in the range 280-660 GHz, ultimately yielding nearly 100 transitions up to
and
. From the combined data set, all three rotational constants and centrifugal distortion terms up to the sextic order were determined to high accuracy, providing a reliable set of frequency predictions to the lower end of the THz band. Isotopic substitution has enabled both a determination of the molecular structure of HCCSH and, by inference, its formation pathway in our nozzle discharge source via the bimolecular radical-radical recombination reaction
, which is calculated to be highly exothermic (−477 kJ/mol) using the HEAT345(Q) thermochemical scheme.