Two absorption features in the archival PRIMOS survey of Sagittarius B2(N) were assigned somewhat tentatively to the N-protonated isocyanic acid, H₂NCO⁺, by
H. Gupta, C. A. Gottlieb, V. Lattanzi, J. C. Pearson, and M. C. McCarthy,
Laboratory Measurements and Tentative Astronomical Identification of H₂NCO⁺,
Astrophys. J. 778, L1 (2013).
The transitions are 1₀₁ – 0₀₀ (para) and 2₁₁ – 1₁₀ (ortho) near 20228 and 40783 GHz, respectively. The amount of spectral lines in that frequency range, in particular those in absorption, are rather small. Moreover, the features show some additional structure caused by ¹⁴N hyperfine structure. Therefore, the identifications is probably quite secure. The rotational temperature was estimated to be close to CMB (2.725 K), possibly slightly higher. This is in accord with the molecule to reside in the not so dense halo of Sgr B2(N) with n(H₂) < 10⁴ cm^–3.

N. Marcelino, M. Agúndez, J. Cernicharo, E. Roueff, and M. Tafalla
reported on the
Discovery of the Elusive Radical NCO and Confirmation of H₂NCO⁺ in Space
Astron. Astrophys. 612, Art. No. L10 (2018).
The cation was detected in the course of a 3 mm line survey of the dense core L483 carried out with the IRAM 30 m telescope. Six a-type transitions with K_a = 0 and 1 and J = 4 – 3 and 5 – 4 were observed with reasonable to good quality. The cation is about a factor of 400 less abundant in this source than HNCO.

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Contributor(s): H. S. P. Müller; 11, 2013; 05, 2018

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