Electron-Impact Dissociation of Hydrocarbon Molecular Ions

Book · Wed Jan 01 04:00:00 EST 2014

OSTI ID:1214455

Bannister, Mark E ^[1]; Schultz, David Robert ^[1]

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1. ORNL

Absolute cross sections for electron-impact dissociation of CH_x^+ (x=1,2,3) producing CH_y^+ (y=0,1,2) fragment ions were measured in the 3-100 eV range using a crossed electron-ion beams technique with total uncertainties of about 11% near the cross section peaks. For CH^+ dissociation, although the measured energy dependence agrees well with two sets of storage ring measurements, the magnitude of the present results lies about 15% to 25% below the other results at the cross section peak near 40 eV. For dissociation of CH_2^+, the cross sections are nearly identical for energies above 15 eV, but they are dramatically different at lower energies. The CH^+ channel exhibits a strong peak rising from an observed threshold of about 6 eV; the C^+ channel is relatively flat down to the lowest measured energy. For dissociation of CH_3^+ and CD_3^+, good agreement is found with other results reported for the CH^+ fragment, but some differences are found for the CD_2^+ and C^+ fragments. A pilot study has also been undertaken to assess the feasibility of applying a molecular dynamics approach to treat the full range of electron-hydrocarbon dissociation processes, especially for energies above a few eV, in order to provide an overarching theoretical model that can be readily applied. Comparison with the experimental data for CH^+ shows favorable agreement.

• Research Organization: Oak Ridge National Laboratory (ORNL); Multicharged Ion Research Facility (MIRF)
• Sponsoring Organization: SC USDOE - Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1214455
• Country of Publication: United States
• Language: English