Carbonic Acid in the Gas Phase and Its Astrophysical Relevance
Wolfgang Hage,
Klaus R. Liedl,
*
Andreas Hallbrucker,
Erwin Mayer
*
In outer space, high-energy irradiation of cryogenic ice mixtures
of abundant water and carbon dioxide is expected to form solid carbonic
acid. Experiments and thermodynamic analyses show that crystalline
carbonic acid sublimates without decomposition. Free-energy
considerations based on highly accurate molecular quantum mechanics, in
combination with vapor pressures resulting from experimental
sublimation rates, suggest that in the gas phase, a monomer and dimer
of carbonic acid are in equilibrium, comparable to that of formic acid.
Gaseous carbonic acid could be present in comets, on Mars and outer
solar system bodies, in interstellar icy grains, and in Earth's upper
atmosphere.
Institut für Allgemeine, Anorganische und Theoretische
Chemie, Universität Innsbruck, A-6020 Innsbruck, Austria.
*
To whom correspondence should be addressed. E-mail:
klaus.liedl{at}vibk.ac.at and erwin.mayer{at}uibk.ac.at
