Experimental Studies of H13CO+ Recombining with Electrons at Energies between 2–50 000 meV

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2014-08, Vol.118 (31), p.6034-6049
• Main Authors: Hamberg, Mathias, Kashperka, Iryna, Thomas, Richard D, Roueff, Evelyne, Zhaunerchyk, Vitali, Danielsson, Mathias, af Ugglas, Magnus, Österdahl, Fabian, Vigren, Erik, Kaminska, Magdalena, Källberg, Anders, Simonsson, Ansgar, Paal, Andras, Gerin, Maryvonne, Larsson, Mats, Geppert, Wolf D
• Format: Article
• Language: English
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp5032306

An investigation into the dissociative recombination process for H13CO+ using merged ion-electron beam methods has been performed at the heavy ion storage ring CRYRING, Stockholm, Sweden. We have measured the branching fractions of the different product channels at ∼0 eV collision energy to be the following: CO + H 87 ± 2%, OH + C 9 ± 2%, and O + CH 4 ± 2%. The formation of electronically excited CO in the dominant reaction channel has also been studied, and we report the following tentative branching fractions for the different CO product electronic states: CO(X 1Σ+) + H, 54 ± 10%; CO(a 3Π) + H, 23 ± 4%; and CO(a′ 3Σ+) + H, 23 ± 4%. The absolute cross section between ∼2–50 000 meV was measured and showed resonance structures between 3 and 15 eV. The cross section was fitted in the energy range relevant to astrophysics, i.e., between 1 and 300 meV, and was found to follow the expression σ = 1.3 ± 0.3 × 10–16 E –1.29±0.05 cm2 and the corresponding thermal rate constant was determined to be k(T) = 2.0 ± 0.4 × 10–7(T/300)−0.79±0.05 cm3 s–1. Radioastronomical observations with the IRAM 30 m telescope of HCO+ toward the Red Rectangle yielded an upper column density limit of 4 × 1011 cm–2 of HCO+ at the 1σ level in that object, indicating that previous claims that the dissociative recombination of HCO+ plays an important role in the production of excited CO molecules emitting the observed Cameron bands in that object are not supported.