On the Energetics of the HCO${}^{+}$ + C $\to$ CH${}^{+}$ + CO Reaction and Some Astrochemical Implications

Abstract

We explore the energetics of the titular reaction, which current astrochemical databases consider open at typical dense molecular (i.e., dark) cloud conditions. As is common for reactions involving the transfer of light particles, we assume that there are no intersystem crossings of the potential energy surfaces involved. In the absence of any such crossings, we find that this reaction is endoergic and will be suppressed at dark cloud temperatures. Updating accordingly a generic astrochemical model for dark clouds changes the predicted gas-phase abundances of 224 species by greater than a factor of 2. Of these species, 43 have been observed in the interstellar medium. Our findings demonstrate the astrochemical importance of determining the role of intersystem crossings, if any, in the titular reaction.

arXiv commentAccepted for publication in ApJ; 14 pages, 2 figures, and 1 table

References in corpus (13)

• The UMIST database for astrochemistry 2012
• A KInetic Database for Astrochemistry (KIDA)
• Non-thermal desorption from interstellar dust grains via exothermic surface reactions
• The 2014 KIDA network for interstellar chemistry
• Chemistry of Dark Clouds: Databases, Networks, and Models
• Astrochemistry of dust, ice and gas: introduction and overview
• Molecular absorption lines toward star-forming regions : a comparative study of HCO+, HNC, HCN, and CN
• The Effects of Molecular Anions on the Chemistry of Dark Clouds
• Origin of CH+ in diffuse molecular clouds warm H2 and ion-neutral drift
• Ion-molecule reactions involving HCO${}^{+}$ and N${}_2$H${}^{+}$: Isotopologue equilibria from new theoretical calculations and consequences for interstellar isotope fractionation
• Reaction Studies of Neutral Atomic $\mathrm{C}$ with ${\mathrm{H}}_3^{+}$ using a Merged-Beams Apparatus
• Merged-beams Reaction Studies of O + H_3^+
• Recommended Thermal Rate Coefficients for the C + H${}_3^{+}$ Reaction and Some Astrochemical Implications