Two absorption features in the archival PRIMOS survey of Sagittarius B2(N)
were assigned somewhat tentatively to the N-protonated isocyanic acid,
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 cm3.