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Title: H{sub 2}(v = 0,1) + C{sup +}({sup 2} P) {yields} H+CH{sup +} STATE-TO-STATE RATE CONSTANTS FOR CHEMICAL PUMPING MODELS IN ASTROPHYSICAL MEDIA

State-to-state rate constants for the title reaction are calculated using the electronic ground state potential energy surface and an accurate quantum wave-packet method. The calculations are performed for H{sub 2} in different rovibrational states, v = 0, 1 and J = 0 and 1. The simulated reaction cross section for v = 0 shows a rather good agreement with the experimental results of Gerlich et al., both with a threshold of 0.36 eV and within the experimental error of 20%. The total reaction rate coefficients simulated for v = 1 are two times smaller than those estimated by Hierl et al. from cross sections measured at different temperatures and neglecting the contribution from v > 1 with an uncertainty factor of two. Thus, part of the disagreement is attributed to the contributions of v > 1. The computed state-to-state rate coefficients are used in our radiative transfer model code applied to the conditions of the Orion Bar photodissociation region, and leads to an increase of the line fluxes of high-J lines of CH{sup +}. This result partially explains the discrepancies previously found with measurements and demonstrates that CH{sup +} excitation is mostly driven by chemical pumping.
Authors:
; ;  [1] ; ;  [2] ;  [3]
  1. Instituto de Fisica Fundamental (IFF-CSIC), C.S.I.C., Serrano 123, E-28006 Madrid (Spain)
  2. Centro de Astrobilogia, CSIC-INTA, Torrejon de Ardoz, Madrid (Spain)
  3. Institut des Sciences Moleculaires, Universite de Bordeaux, CNRS UMR 5255, 351 cours de la Liberation, F-33405 Talence Cedex (France)
Publication Date:
OSTI Identifier:
22167529
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 766; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTROPHYSICS; CROSS SECTIONS; DISSOCIATION; ERRORS; EV RANGE; EXCITATION; GROUND STATES; HYDROGEN; PHOTOLYSIS; POTENTIAL ENERGY; PUMPING; RADIANT HEAT TRANSFER; REACTION KINETICS; SURFACE ENERGY; WAVE PACKETS