Detection of HNCOH+ in the interstellar medium
Year: 2026
Type: article
Abstract: Only five out of the ∼350 molecules detected in the interstellar medium (ISM) carry the isocyanate functional group (NCO), the essential substructure of peptide bonds in proteins. Among them are isocyanic acid (HNCO) and its most stable N-protonated isomer, H_2NCO+$. Previous studies have predicted that the O-protonated isomer HNCOH$^+ should be present in the ISM; yet this species has remained elusive. We search for the metastable HNCOH+$ towards the Galactic centre molecular cloud G+0.693-0.027, where H_2NCO$^+ has already been detected. We use an ultra-deep broadband spectral survey carried out towards G+0.693-0.027 with the Yebes 40-m, IRAM 30-m, and APEX telescopes covering nearly 150 GHz of bandwidth between 31 and 275 GHz. We report the first detection of HNCOH+$ in the ISM with a column density of N = (9.9 ± 0.5)times10^12 cm^-2, which corresponds to a molecular abundance relative to H_2 of (7.3^ +1.3 _ -1.0 )times10^-11. With the measured H_2NCO^+ column density of N = (2.6 ± 0.3) times 10^ 12 cm^-2, this yields a HNCOH^+/H_2NCO^+ ratio of 3.8^ +0.5 _ -0.4 . This result is consistent with recent kinetic calculations that favour the formation of HNCOH^+ over H_2NCO$^+. The detection of HNCOH+ in the ISM broadens the inventory of molecules known to contain the isocyanate functional group and reinforces recent works showing that isomer abundances in the ISM do not necessarily correlate with thermodynamic stability.
Source: Astronomy and Astrophysics
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
Awards: G10949448, G1152523013, G121809054, G1272900390, G1274526653, G1348953298, G1397962376, G1401168639, G1507096846, G1622782223, G1743472294, G1910261178, G205929289, G2290189609, G2309174360, G2660406951, G3443738222, G3518538256, G3702198118, G3926388292, G4212894969, G4240073238, G4515945706, G4944594896, G5099673792, G5404395142, G5542129504, G5572486069, G5635532810, G582065459, G5934669618, G5955501538, G6033112984, G6719929187, G7097722406, G7395345766, G745419941, G7805626310, G7915813472, SFB 1601: Die kosmische Entwicklung der Lebensräume massereicher Sterne, G8575141037, G8667377315, G8709270594, G8829154781, G8920660035, G897484643, G9000362223
OpenAlex ID: W7224950296