THE LOW-TEMPERATURE NUCLEAR SPIN EQUILIBRIUM OF H super(+) sub(3) IN COLLISIONS WITH H sub(2)
Recent observations of H sub(2) and H super(+) sub(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 super(+) sub(3) and H sub(2) should undergo frequent thermalizing collisions in mo...
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| Veröffentlicht in: | The Astrophysical journal 2012-11, Vol.759 (1), p.1-5 |
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| container_title | The Astrophysical journal |
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| creator | GRUSSIE, F Berg, M H Crabtree, K N Gartner, S McCall, B J Schlemmer, S Wolf, A Kreckel, H |
| description | Recent observations of H sub(2) and H super(+) sub(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 super(+) sub(3) and H sub(2) should undergo frequent thermalizing collisions in molecular clouds. Non-thermal behavior of the fundamental H super(+) sub(3)/H sub(2 ) 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 super(+) sub(3) in collisions with H sub(2) 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. |
| doi_str_mv | 10.1088/0004-637X/759/1/21 |
| format | Article |
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| source | EZB-FREE-00999 freely available EZB journals; Institute of Physics Open Access Journal Titles; Alma/SFX Local Collection |
| subjects | Collisions Diffusion Interstellar Interstellar matter Molecular clouds Nuclear spin Populations Radiofrequency |
| title | THE LOW-TEMPERATURE NUCLEAR SPIN EQUILIBRIUM OF H super(+) sub(3) IN COLLISIONS WITH H sub(2) |
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