2026-05-05T18:43:29Zhttps://uvadoc.uva.es/oai/request

oai:uvadoc.uva.es:10324/610532025-12-01T11:24:49Zcom_10324_1186com_10324_931com_10324_894col_10324_1404

00925njm 22002777a 4500 dc Sanz Novo, Miguel author Rivilla, Víctor M. author Jiménez Serra, Izaskun author Martín Pintado, Jesús author Colzi, Laura author Zeng, Shaoshan author Megías, Andrés author López Gallifa, Álvaro author Martínez Henares, Antonio author Massalkhi, Sarah author Tercero, Belén author Vicente, Pablo de author Martín, Sergio author Andrés, David San author Requena Torres, Miguel A. author 2023 A quarter century after the detection of the last interstellar carboxylic acid, acetic acid (CH3COOH), we report the discovery of a new one, the cis-trans form of carbonic acid (HOCOOH), toward the Galactic center molecular cloud G+0.693–0.027. HOCOOH stands as the first interstellar molecule containing three oxygen atoms and the third carboxylic acid detected so far in the interstellar medium. Albeit the limited available laboratory measurements (up to 65 GHz), we have also directly identified several pairs of unblended lines in the astronomical data (between 75 and 120 GHz), which allowed us to slightly improve the set of spectroscopic constants. We derive a column density for cis-trans HOCOOH of N = (6.4 ± 0.4) × 1012 cm−2, which yields an abundance with respect to molecular H2 of 4.7 × 10−11. Meanwhile, the extremely low dipole moment (about 15 times lower) of the lower-energy conformer, cis-cis HOCOOH, precludes its detection. We obtain an upper limit to its abundance with respect to H2 of ≤1.2 × 10−9, which suggests that cis-cis HOCOOH might be fairly abundant in interstellar space, although it is nearly undetectable by radio astronomical observations. We derive a cis-cis/cis-trans ratio of ≤25, consistent with the smaller energy difference between both conformers compared with the relative stability of trans- and cis-formic acid. Finally, we compare the abundance of these acids in different astronomical environments, further suggesting a relationship between the chemical content found in the interstellar medium and the chemical composition of the minor bodies of the solar system, which could be inherited during the star formation process. The Astrophysical Journal, 2023, Volume 954, Number 1 0004-637X https://uvadoc.uva.es/handle/10324/61053 10.3847/1538-4357/ace523 3 1 The Astrophysical Journal 954 1538-4357 Discovery of the Elusive Carbonic Acid (HOCOOH) in Space