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A: Atomphysik
A 13: Ion-Atom/Molekuel/Ion-Stoesse
A 13.2: Talk
Thursday, March 25, 2004, 11:15–11:30, HS 132
Break-up of molecular hydrogen in singly ionising collisions with fast protons — •Christina Dimopoulou1, C. Hoehr1, D. Fischer1, R. Moshammer1, A. Dorn1, C.D. Schroeter1, J.R. Crespo Lopez-Urrutia1, H. Kollmus2, R. Mann2, S. Hagmann2, P. Fainstein3, and J. Ullrich1 — 1Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg — 2Gesellschaft fuer Schwerionenforschung, Planckstrasse 1, D-64291 Darmstadt — 3Centro Atomico Bariloche, Avenida E.Bustillo 9500-8400, Bariloche, Argentina
Single ionisation of H2 by 6 MeV proton impact has been studied in a kinematically complete experiment using the COLTRIMS technique (reaction-microscope). There are two basic channels in the single ionisation of H2 : in the first case a H2+ ion is formed (”pure” ionisation), whereas, with a small probability, single ionisation is accompanied by dissociation into a proton and a H atom (ground state dissociation). For both channels, the emitted electron and the recoil ion have been recorded in coincidence. Thus, the electron energy distributions for pure ionisation and that coincident with dissociation have been measured. Surprisingly, significant differences are observed though the kinetic energy released in the dissociation amounts to only a few tens of meV. In the case of pure ionisation of H2 fully differential cross-sections for low-energy electrons have been measured as well. Furthermore, in the case of ground state dissociation we have been able to determine the orientation of the molecule. Thus, electron emission spectra for fixed-in-space H2 have been analysed. The experimental results will be presented and discussed. Whenever possible, a comparison with theoretical calculations has been made as well.