2024A&A...682L...4C

We present the first detection of HCNS (thiofulminic acid) in space with the QUIJOTE line survey in the direction of TMC-1. We performed a complete study of the isomers of CHNS and CHNO, including NCO and NCS. The derived column densities for HCNS, HNCS, and HSCN are (9.0 ± 0.5) × 10⁹, (3.2 ± 0.1) × 10¹¹, and (8.3 ± 0.4) × 10¹¹ cm^–2, respectively. The HNCS/HSCN abundance ratio is 0.38. The abundance ratios HNCO/HNCS, HCNO/HCNS, HOCN/HSCN, and NCO/NCS are 34 ± 4, 8.3 ± 0.7, 0.18 ± 0.03, and 0.78 ± 0.07, respectively. These ratios cannot be correctly reproduced by our gas-phase chemical models, which suggests that formation paths for these species are missing, and/or that the adopted dissociative recombination rates for their protonated precursors have to be revised. The isotopologues H¹⁵NCO, DNCO, HN¹³CO, DCNO, H³⁴SCN, and DSCN have also been detected with the ultrasensitive QUIJOTE line survey.