===== On the Detection of HCNS Isomers in the Interstellar Medium ===== ==== Isothiocyanic acid ==== **HNCS**, the lowest energy isomer, was detected in the Galactic center source Sgr B2(OH) by\\ M. A. Frerking, R. A. Linke, and P. Thaddeus,\\ **[[https://doi.org/10.1086/183126|Interstellar Isothiocyanic Acid]]**\\ //Astrophys. J.// **234**, (1979), L143.\\ They detected 5 successive //Ka// = 0 //a//-type transitions with //J// = 7 – 6 to 12 – 11. The molecule is only abundant in the colder parts of the source.\\ \\ The detection in Sgr B2 is described below in the HSCN section.\\ \\ G. R. Adande, D. T. Halfen, L. M. Ziurys, D. Quan, and E. Herbst\\ report on\\ **[[https://doi.org/10.1088/0004-637X/725/1/561|Observations of the [HNCS]/[HSCN] Ratio in Sgr B2 and TMC-1: Evidence for Low-temperature Gas-phase Chemistry]]**\\ //Astrophys. J.// **725**, (2010), 561.\\ The 12 m ARO telescope probably probes the envelope of Sgr B2, where they found ratios of 2 to 7, whereas they found a ratio close to 1 in the dark molecular cloud TMC-1.\\ \\ L. Velilla Prieto, C. Sánchez Contreras, J. Cernicharo, M. Agúndez, G. Quintana-Lacaci, J. Alcolea, V. Bujarrabal, F. Herpin, K. M. Menten, and F. Wyrowski\\ report on\\ **[[https://doi.org/10.1051/0004-6361/201424768|New N-bearing species towards OH 231.8+4.2 — HNCO, HNCS, HC3N, and NO]]**\\ //Astron. Astrophys.// **575**, (2015), Art. No. A84.\\ The molecules were identified in the course of a line survey of the circumstellar envelope of this O-rich AGB star, aka QX Pup, with the IRAM 30 m dish at 3 to 1 mm.\\ \\ M. Sanz-Novo, V. M. Rivilla, I. Jiménez-Serra, J. Martín-Pintado, L. Colzi, S. Zeng, A. Megías, Á. López-Gallifa, A. Martínez-Henares, S. Massalkhi, B. Tercero, P. de Vicente, D. San Andrés, S. Martín, and M. A. Requena-Torres\\ announced the\\ **[[https://doi.org/10.3847/1538-4357/ad2c01|Interstellar Detection of O-protonated Carbonyl Sulfide, HOCS+]]**\\ //Astrophys. J.// **965**, Art. No. 149 (2024).\\ The results were obtained in the course of a molecular line survey of the Galactic Center molecular cloud G+0.693–0.027 employing the Yebes 40 m and IRAM 30 m radio telecopes. The //Ka// = 0 lines of HOCS+ were blended with those of HNC34S because of nearly identical values of //B + C//. The transitions cover 34 to 161 GHz with //J"// = 2, 3, 6 − 13. The contribution of HNC34S could be accounted for accurately through lines of HNCS, OCS, and OC34S and turned out to be less than that of HOCS+. Several lines are slightly or more severely blended in addition, but this is in most cases also well accounted.\\ \\ ---- Contributor(s): H. S. P. Müller; 09, 2009; 02, 2024; 04, 2024 ---- ==== Thiocyanic acid ==== The detection of **HSCN**, the second isomer, has been reported by\\ D. T. Halfen, L. M. Ziurys, S. Brünken, C. A. Gottlieb, M. C. McCarthy, and P. Thaddeus,\\ **[[https://doi.org/10.1088/0004-637X/702/2/L124|Detection of a New Interstellar Molecule: Thiocyanic Acid HSCN]]**\\ //Astrophys. J.// **702**, (2009), L124.\\ The Arizona Radio Observatory 12 m telescope has been employed to detect the //Ka// = 0, //J// = 6 – 5 to 12 – 11 transitions; the next two transitions were also sought for, but were too weak to be detected, indicating again fairly low rotational temperatures. Observations have been made toward the Galactic center source Sgr B2(N). Though more than 3000 K higher in energy than HNCS, it is only lower in abundance by a factor of three. HNCS was also detected in this source.\\ \\ J. Cernicharo, M. Agúndez, C. Cabezas, B. Tercero, R. Fuentetaja, N. Marcelino, and P. de Vicente \\ announced the\\ **[[https://doi.org/10.1051/0004-6361/202349105|Discovery of thiofulminic acid with the QUIJOTE line survey: A study of the isomers of HNCS and HNCO in TMC-1]]**\\ //Astron. Astrophys.// **682**, (2024), Art. No. L4.\\ The authors detect DSCN and H34SCN, which are about a factor of 40 lower in abundance that the main isotopolog.\\ \\ ---- Contributor(s): H. S. P. Müller; 09, 2009; 02, 2024 ---- ==== Thiofulminic acid ==== J. Cernicharo, M. Agúndez, C. Cabezas, B. Tercero, R. Fuentetaja, N. Marcelino, and P. de Vicente \\ announced the\\ **[[https://doi.org/10.1051/0004-6361/202349105|Discovery of thiofulminic acid with the QUIJOTE line survey: A study of the isomers of HNCS and HNCO in TMC-1]]**\\ //Astron. Astrophys.// **682**, (2024), Art. No. L4.\\ The molecule was identified in the course of a line survey carried out with the Yebes 40 m and IRAM 30 m dishes. Three transitions, //J// = 3 − 2 (~36.9 GHz), 4 − 3 (~49.2 GHz), and 6 − 5 (~73.8 GHz) were detected with good to reasnable signal-to-noise ratios. HNCS is anout a factor of 36 more abundant, while for HSCN the factor is about 92.\\ \\ ---- Contributor(s): H. S. P. Müller; 02, 2024 ----