Laboratory measurements and tentative astronomical identification of H2NCO+.
GUPTA H., GOTTLIEB C.A., LATTANZI V., PEARSON J.C. and McCARTHY M.C.
Abstract (from CDS):
The rotational spectrum of H2NCO+, the ground-state isomer of protonated HNCO, has been measured in a molecular beam in the centimeter band with a Fourier transform microwave spectrometer and in a low-pressure laboratory discharge in absorption in the millimeter band. Spectroscopic constants, including the nitrogen-14 hyperfine coupling constant, derived from 30 a-type transitions between 20 and 367 GHz with J ≤ 18 and Ka ≤ 3 allow the principal rotational transitions to be calculated to 1 km/s or better in equivalent radial velocity well into the far IR. Two low-lying rotational transitions of H2NCO+ in the centimeter band (0_0, 0–10, 1_ and 1_1, 0–21, 1_) were tentatively identified in absorption in the PRIMOS spectral line survey of Sgr B2(N) with the Green Bank Telescope. The lines of H2NCO+ arise in a region of the Sgr B2(N) halo whose density is low (n < 1x104/cm3). The derived column density of (6-14)x1011/cm2 implies that the fractional abundance is ∼10–12. Owing to the ubiquity of HNCO in galactic molecular clouds, H2NCO+ is a good candidate for detection in sources spanning a wide range of physical conditions.