State Selective Single-Electron Capture in the Collisions C^q++He, (q=1-6) at Low to Intermediate Velocities

M.A. Abdallah¹, W. Wolff², H.E. Wolf², C.L. Cocke³, M.P. Stöckli³, E. Üdgo³, S. Datz¹, E.Y. Kamber⁴

¹ Oak Ridge National Laboratory, Oak Ridge, TN
² U. Federal do Rio de Janeiro, Brazil
³ James R. Macdonald Laboratory, Kansas State University, Manhattan, Ks
⁴ Western Michigan U.

The process of single-electron capture is studied in the collision systems C^q++He, q=1-6, at collision velocities between 0.25 and 1.67 a.u. using the technique of cold-target recoil-ion momentum spectroscopy (COLTRIMS). Final states are resolved by means of energy defect (Q-value). The angular distributions are measured for every resolved state. The tendency of broadening of the reaction window with increasing collision velocity is observed in C³⁺-C⁶⁺ collisions. A significant fraction of core rearrangement is observed for C⁺-C³⁺. As seen in the angular distributions, this core rearrangement happens for collisions with relatively small impact parameters. The contributions from metastable states in C⁺ and C²⁺ are separated. In C²⁺, metastable states ions display a stronger velocity dependence for single capture cross section than ions in ground states. In C⁺ this strong velocity dependence is not observed. Results are compared to earlier experiments and theoretical calculations.

Supported by the US DOE; MAA is supported in part by the ORNL Postdoctoral Research Associates Program administrated jointly by Oak Ridge Institute for Science and Education and Oak Ridge National Lab.

 

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