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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents



ID: 660929.0, MPI für Astronomie / Publikationen_mpia
The low-temperature nuclear spin equilibrium of H+ 3 in collisions with H2
Authors:Grussie, F.; Berg, M. H.; Crabtree, K. N.; Gärtner, S.; McCall, B. J.; Schlemmer, S.; Wolf, A.; Kreckel, H.
Date of Publication (YYYY-MM-DD):2012
Journal Abbrev.:The Astrophysical Journal
Volume:759
Issue / Number:1
Start Page:id. 21
Audience:Not Specified
Abstract / Description:Recent observations of H2 and H+ 3 in diffuse interstellar sightlines revealed a difference in the nuclear spin excitation temperatures of the two species. This discrepancy comes as a surprise, as H+ 3 and H2 should undergo frequent thermalizing collisions in molecular clouds. Non-thermal behavior of the fundamental H+ 3/H2 collision system at low temperatures was considered as a possible cause for the observed irregular populations. Here, we present measurements of the steady-state ortho/para ratio of H+ 3 in collisions with H2 molecules in a temperature-variable radiofrequency ion trap between 45 and 100 K. The experimental results are close to the expected thermal outcome and they agree very well with a previous micro-canonical model. We briefly discuss the implications of the experimental results for the chemistry of the diffuse interstellar medium.
Free Keywords:astrochemistry; ISM: molecules; molecular processes
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:URL:http://cdsads.u-strasbg.fr/abs/2012ApJ...759...21G
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