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D. L. Huestis (SRI)
For the past 30 years, models of outer planet ionospheres have used estimated rate coefficients for charge transfer Reaction (1), which is a critical step in controlling the electron density. No confirmation has been available from the laboratory or theory.
(1) H+ + H2(v{\geq}4) arrow H + H2+
By analysis and extrapolation of the results from recent theoretical work [1,2] from the plasma fusion community, we suggest that Reaction (1) has a rate coefficient of approximately 1.3 \times 10-9 cm3/s, consistent with numbers in current models.
In addition, we suggest that vibrational relaxation Reaction (2) will also be fast, with rate coefficients of approximately 1.5 \times 10-9 cm3/s for v = 4-8 and 2.8 \times 10-9 cm3/s for v = 1-3.
(2) H+ + H2(vi) arrow H+ + H2(vf < vi)
Inclusion of Reaction (2) will significantly reduce calculated vibrational temperatures in ionospheric models. Protons are less abundant than neutral hydrogen atoms by a factor of about 10,000 and the proton rate coefficients for vibrational relaxation are about a factor of 10,000 larger.
[1] A. Ichihara, O. Iwamoto, and R. K. Janev, ``Cross Sections for the Reaction H+ + H2(v=0-14) arrow H + H2+ at Low Collision Energies," J. Phys. B. 33, 4747-4758 (2000).
[2] P.S. Krstic, ``Inelastic Processes from Vibrationally Excited States in Slow H+ + H2 and H + H2+ Collisions: Excitations and Charge Transfer," Phys. Rev. A 66, 042717 (2002).
The author(s) of this abstract have provided an email address for comments about the abstract: david.huestis@sri.com
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.