title: Transfer of a proton between H2 and O2.
abstract: The proton affinities of hydrogen and oxygen are very similar. Therefore, it has been discussed that the proton transfer from the omnipresent H(3)(+) to molecular oxygen in the near thermoneutral reaction H(3)(+) + O(2) <--> O(2)H(+) + H(2) effectively binds the interstellar oxygen in O(2)H(+). In this work, the proton transfer reaction has been investigated in a low-temperature 22-pole ion trap from almost room temperature (280 K) down to the lowest possible temperature limited by freeze out of oxygen gas (about 40 K at a low pressure). The Arrhenius behaviour of the rate coefficient for the forward reaction shows that it is subject to an activation energy of E(A)/k=113 K. Thus, the forward reaction can proceed only in higher temperature molecular clouds. Applying laser-induced reactions to the given reaction (in the backward direction), a preliminary search for spectroscopic signatures of O(2)H(+) in the infrared was unsuccessful, whereas the forward reaction has been successfully used to probe the population of the lowest ortho and para levels of H(3)(+).
authors.affiliation: I. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Kluge
authors.forename: Sabrina
authors.initials: S
authors.lastname: Gärtner
authors.forename: Sandra
authors.initials: S
authors.lastname: Brünken
authors.forename: Oskar
authors.initials: O
authors.lastname: Asvany
authors.forename: Dieter
authors.initials: D
authors.lastname: Gerlich
authors.forename: Stephan
authors.initials: S
authors.lastname: Schlemmer