Collision-induced dissociation and dissociative capture of diatomic molecular ions at keV energies

D. Hathiramani, K.D. Carnes, J.W. Maseberg, I. Ben-Itzhak
(J.R.Mcdonald Laboratory, Department of Physics, Kansas State University),

T. Kitamura
(Department of Chemistry, Tokyo Metropolitan University, Japan)

During an impact between a diatomic molecular ion AB+ and an atomic target C at collision energies of a few keV the two main processes are: (1) collision-induced dissociation (CID) AB+ + C → A+ + B + C or A + B+ + C and (2) dissociative capture (DC) AB+ + C → A + B + C+. We have developed a 3D momentum imaging system for the fragments, which allows us to study the CID and the DC of simple diatomic molecular ions like H2+, HD+ and HeH+ on a rare gas target at collision energies of about 2 keV/amu. Using an electric field in the target region followed by a field free region, we managed to separate the CID from the DC in time. Furthermore, it is possible to evaluate the relative importance of these two processes, because both CID and DC are measured simultaneously. Moreover, the cross section ratio of the two possible CID channels can be obtained for heteronuclear molecules. The dependence of DC and CID on the molecular alignment is under investigation for the simplest molecular ion H2+.

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.

Submitted to DAMOP 2002, May 2002 in Williamsburg, VA.

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