Dissociative Recombination and Excitation of CH{sup {plus}} {sub 5} : Absolute Cross Sections and Branching Fractions
- Department of Physics I, Royal Institute of Technology, S-10044, Stockholm (Sweden)
- Department of Physics, Stockholm University, P.O. Box 6730, S-11385, Stockholm (Sweden)
- FOM Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ Amsterdam (The Netherlands)
- Manne Siegbahn Laboratory, Stockholm University, S-10405 Stockholm (Sweden)
- JILA, University of Colorado, Campus Box 440, Boulder, Colorado 80309-0390 (United States)
- Physics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6377 (United States)
The heavy-ion storage ring CRYRING was used to measure the absolute dissociative recombination and dissociative excitation cross sections for collision energies below 50 eV. Deduced thermal rates coefficients are consistent with previous beams data but are lower by a factor of 3 than the rates measured by means of the flowing afterglow Langmuir probe technique. A resonant structure in dissociative recombination cross section was found at 9 eV. We have determined the branching fractions in DR of CH{sup {plus}} {sub 5} below 0.2 eV. The branching is dominated by three-body CH{sub 3} + H + H and CH{sub 2} + H{sub 2} + H dissociation channels, which occur with branching ratios of {approx}0.7 and {approx}0.2, respectively; thus methane is a minor species among dissociation products. Both the measured absolute cross sections and branching in dissociative recombination of CH{sup {plus}} {sub 5} can have important implications for the models of dense interstellar clouds and abundance of CH{sub 2}, CH{sub 3} and CH{sub 4} in these media. {copyright} {ital {copyright} 1998.} {ital The American Astronomical Society}
- OSTI ID:
- 642669
- Journal Information:
- Astrophysical Journal, Vol. 498, Issue 2; Other Information: PBD: May 1998
- Country of Publication:
- United States
- Language:
- English
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