===== On the Detection of Carbonic Acid in Space =====

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 \\
**[[https://doi.org/10.3847/1538-4357/ace523|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<sub>a</sub>// ≤ 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<sub>c</sub>//. 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.\\
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Contributor(s): H. S. P. Müller; 08, 2023

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