title: A reanalysis of the HCO+/HOC+ abundance ratio in dense interstellar clouds.
abstract: New theoretical and experimental results have prompted a reinvestigation of the HCO+/HOC+ abundance ratio in dense interstellar clouds.  These results pertain principally but not exclusively to the reaction between HOC+ and H2, which was previously calculated by DeFrees, McLean, and Herbst to possess a large activation energy barrier.  New calculations, reported here, indicate that this activation energy barrier is quite small and may well be zero.  In addition, experimental results at higher energy and temperature indicate strongly that the reaction proceeds efficiently at interstellar temperatures.  If HOC+ does indeed react efficiently with H2 in interstellar clouds, the calculated HCO+/HOC+ abundance ratio rises to substantially greater value under standard dense cloud conditions than in deduced via the tentative observation of HOC+ in Sgr B2.
authors.affiliation: Department of Chemistry, University of California, Santa Barbara, USA.
authors.forename: M F
authors.initials: MF
authors.lastname: Jarrold
authors.forename: M T
authors.initials: MT
authors.lastname: Bowers
authors.forename: D J
authors.initials: DJ
authors.lastname: DeFrees
authors.forename: A D
authors.initials: AD
authors.lastname: McLean
authors.forename: E
authors.initials: E
authors.lastname: Herbst
mesh_terms: D055580:Astronomical Phenomena; D001256:Astronomy; D019443:Cosmic Dust / Q000032:analysis*; D004735:Energy Transfer; D005118:Extraterrestrial Environment; D006838:Hydrocarbons / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D008433:Mathematics; D008956:Models, Chemical; D011789:Quantum Theory; D013696:Temperature
chemical_list: D019443:Cosmic Dust; D006838:Hydrocarbons; D006859:Hydrogen