Advancing spectroscopic understanding of HOCS${}^{+}$: Laboratory investigations and astronomical implications

Abstract

Sulphur-bearing species play crucial roles in interstellar chemistry, yet their precise characterisation remains challenging. Here, we present laboratory experiments aimed at extending the high-resolution spectroscopy of protonated carbonyl sulphide (HOCS${}^{+}$), a recently detected molecular ion in space. Using a frequency-modulated free-space absorption spectrometer, we detected rotational transitions of HOCS${}^{+}$ in an extended negative glow discharge with a mixture of H${}_2$ and OCS, extending the high-resolution rotational characterisation of the cation well into the millimetre wave region (200-370 GHz). Comparisons with prior measurements and quantum chemical calculations revealed an overall agreement in the spectroscopic parameters. With the new spectroscopic dataset in hand, we re-investigated the observations of HOCS${}^{+}$ towards G+0.693-0.027, which were initially based solely on K${}_a$ = 0 lines contaminated by HNC${}^{34}$S. This re-investigation enabled the detection of weak K${}_a$ = 0 transitions, free from HNC${}^{34}$S contamination. Our high-resolution spectroscopic characterisation also provides valuable insights for future millimetre and submillimetre astronomical observations of these species in different interstellar environments. In particular, the new high-resolution catalogue will facilitate the search for this cation in cold dark clouds, where very narrow line widths are typically observed.

9 pages, 3 figures, and 3 tables. Accepted for publication in Astronomy & Astrophysics

References in corpus (19)

• The largest oxigen bearing organic molecule repository
• Modeling Sulfur Depletion in Interstellar Clouds
• Tracing shocks and photodissociation in the Galactic center region
• Yebes 40 m radio telescope and the broad band NANOCOSMOS receivers at 7 mm and 3 mm for line surveys
• Discovery in space of ethanolamine, the simplest phospholipid head group
• Thiols in the ISM: first detection of HC(O)SH and confirmation of C${}_2$H${}_5$SH
• TMC-1, the starless core sulfur factory: Discovery of NCS, HCCS, H2CCS, H2CCCS, and C4S and detection of C5S
• Prebiotic precursors of the primordial RNA world in space: Detection of NH${}_2$OH
• Efficient Production of S${}_8$ in Interstellar Ices: The effects of cosmic ray-driven radiation chemistry and non-diffusive bulk reactions
• Evolution of CO${}_2$, CH${}_4$, and OCS abundances relative to H${}_2$O in the coma of comet 67P around perihelion from Rosetta/VIRTIS-H observations
• Gas phase Elemental abundances in Molecular cloudS (GEMS) VII. Sulfur elemental abundance
• Probing the chemical complexity of amines in the ISM: detection of vinylamine (C${}_2$H${}_3$NH${}_2$) and tentative detection of ethylamine (C${}_2$H${}_5$NH${}_2$)
• Precursors of fatty alcohols in the ISM: Discovery of n-propanol
• Discovery of the elusive carbonic acid (HOCOOH) in space
• First detection of C${}_2$H${}_5$NCO in the ISM and search of other isocyanates towards the G+0.693-0.027 molecular cloud
• Detection of the cyanomidyl radical (HNCN): a new interstellar species with the NCN backbone
• Amides inventory towards the G+0.693-0.027 molecular cloud
• Discovery of thionylimide, HNSO, in space: the first N-, S- and O-bearing interstellar molecule
• Rotational spectroscopic characterisation of the [D2,C,S] system: an update from the laboratory and theory

Cited by in corpus (1)

• Conformational isomerism of methyl formate: new detections of the higher-energy trans conformer and theoretical insights