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, S. Martín, D. S. Andrés, and M. A. Requena-Torres
announced the
Discovery of the Elusive Carbonic Acid (HOCOOH) in Space,
Astrophys. J. 954, Art. No. 3 (2023)
The molecule was detected 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 telecopse. The transitions cover 40 to 111 GHz with 2 ≤ J ≤ 9 and K_a ≤ 4. Five lines have good signal-to-noise ratios (S/N) and are unblended or only slightly blended. Some additional ones are more blended or have a less favorable S/N, but strengthen the detection somewhat. As an oblate rotor fairly close to the symmetric limit, the lines frequently consist of quartets of b- and a-type transitions having the same J and K_c. The detected cis-trans conformer is slightly higher in energy than the cis-cis conformer, however, this latter conformer has a much lower dipole moment. Cis-trans carbonic acid is about a factor of ~6.5 and ~31 less abundant than acetic and formic acid, respectively. The cis-cis conformer may reduce these factors by a factor of around 1.5, possibly more.

Contributor(s): H. S. P. Müller; 08, 2023