Faure, A;
Halvick, P;
Stoecklin, T;
Honvault, P;
Epee, MDE;
Mezei, JZ;
Motapon, O;
... Zanchet, A; + view all
(2017)
State-to-state chemistry and rotational excitation of CH+ in photon-dominated regions.
Monthly Notices of the Royal Astronomical Society
, 469
(1)
pp. 612-620.
10.1093/mnras/stx892.
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Abstract
We present a detailed theoretical study of the rotational excitation of CH+ due to reactive and non-reactive collisions involving C+( 2P), H2, CH+, H and free electrons. Specifically, the formation of CH+ proceeds through the reaction between C+( 2P) and H2(νH2 = 1, 2), while the collisional (de)excitation and destruction of CH+ is due to collisions with hydrogen atoms and free electrons. State-to-state and initial-state-specific rate coefficients are computed in the kinetic temperature range 10–3000 K for the inelastic, exchange, abstraction and dissociative recombination processes using accurate potential energy surfaces and the best scattering methods. Good agreement, within a factor of 2, is found between the experimental and theoretical thermal rate coefficients, except for the reaction of CH+ with H atoms at kinetic temperatures below 50 K. The full set of collisional and chemical data are then implemented in a radiative transfer model. Our non-LTE calculations confirm that the formation pumping due to vibrationally excited H2 has a substantial effect on the excitation of CH+ in photondominated regions. In addition, we are able to reproduce, within error bars, the far-infrared observations of CH+ towards the Orion Bar and the planetary nebula NGC 7027. Our results further suggest that the population of νH2 = 2 might be significant in the photon-dominated region of NGC 7027.
| Type: | Article |
|---|---|
| Title: | State-to-state chemistry and rotational excitation of CH+ in photon-dominated regions |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1093/mnras/stx892 |
| Publisher version: | http://doi.org/10.1093/mnras/stx892 |
| Language: | English |
| Additional information: | © 2017 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | Science & Technology, Physical Sciences, Astronomy & Astrophysics, astrochemistry, line: formation, molecular data, molecular processes, radiative transfer, ISM: molecules, BAR PHOTODISSOCIATION REGION, VIBRATIONALLY EXCITED H-2, ORION BAR, DISSOCIATIVE RECOMBINATION, REACTIVE COLLISIONS, LOW-TEMPERATURE, CROSS-SECTION, PDR SURFACE, NGC 7027, H-ATOMS |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/1551341 |
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