Dissociative Capture and Collision Induced Dissociation for Few keV H₂⁺ Impact on Atoms

Nora G. Johnson, A. Max Sayler, Sam Fahrenholtz, D. Hathiramani, J.W. Maseberg, K.D. Carnes, I. Ben-Itzhak
James R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, KS, USA

Dissociative capture [DC, e.g. H₂⁺ + Ar(He) ⇒ H + H + Ar⁺(He⁺)] and collision induced dissociation [CID, e.g. H₂⁺ + Ar(He) ⇒ H⁺ + H + Ar(He)] are measured and separated by a 3D momentum imaging technique. Electronic and vibrational excitation mechanisms are identified for CID via the kinetic energy release and momentum transfer to the center of mass of the molecular ion. Regarding DC, repulsive b³Σ_u⁺ and predissociating c³Π_u final states are distinguished. Angular studies show that DC and electronically excited CID events occur preferentially for molecular ions aligned parallel to their velocity. In contrast, the vibrationally excited CID events occur more readily when the molecular ions are perpendicularly aligned.

This work was supported by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy.

Presented at ISIAC, August 2007 in Crete, Greece.

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