HOC+ + H2 Isomerization Rate at 25 K: Implications for the Observed [HCO+]/[HOC+] Ratios in the Interstellar Medium
Abstract
The recent detection of the metastable HOC+ isomer toward a wide range of interstellar environments has demonstrated abundances that cannot be explained within current chemical models. The abundance of HOC+ in these models relies heavily on the rate of the isomerization of HOC+ by H2 to the lowest energy isomer, HCO+. A variable temperature 22-pole ion-trap apparatus is employed to study the isomerization of HOC+ by H2 at 25 K. The observed rate coefficient for isomerization is (3.8+/-0.5)×10-10 cm3 s-1. This indicates that there is probably no temperature dependence in this reaction below 300 K, suggesting the absence of any significant energetic barrier on the lowest adiabatic H3CO+ potential surface. This result argues that in regions where abundant HOC+ is observed, the production of this isomer must be strongly favored or that there is a concomitant rapid physicochemical loss for the isomer HCO+. Some results for forming DCO+ are briefly mentioned.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 2002
- DOI:
- 10.1086/344404
- Bibcode:
- 2002ApJ...578L..87S
- Keywords:
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- Astrochemistry;
- ISM: Molecules;
- Methods: Laboratory;
- Molecular Processes