Berlin 2005 – wissenschaftliches Programm
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A: Atomphysik
A 8: Poster HU 1
A 8.39: Poster
Samstag, 5. März 2005, 08:30–18:30, Poster HU
Break-up of H2 in singly ionizing collisions with fast protons. — •Christina Dimopoulou1, R. Moshammer1, D. Fischer1, C. Höhr1, A. Dorn1, P.D. Fainstein2, J. R. Crespo López Urrutia1, C.D. Schröter1, S. Hagmann3, H. Kollmus3, R. Mann3, and J. Ullrich1 — 1Max-Planck-Institut für Kernphysik, Saupfercheckweg 1,D-69117 Heidelberg — 2Centro Atómico Bariloche, 8400 Bariloche, Argentina — 3Gesellschaft für Schwerionenforschung, Planckstr.1, D-64291 Darmstadt
Single ionization of H2 by 6 MeV proton impact has been studied in a kinematically complete experiment using the COLTRIMS technique (reaction-microscope). Basically, two channels contribute: in the first case a H2+ ion is formed after the collision ("pure" ionization), whereas, with a small probability, the molecule dissociates into a proton and a H-atom (ground state dissociation)[1]. For both reaction pathways, the momenta of the electron and the recoil ion have been recorded in coincidence. Thus, electron energy distributions have been obtained. For pure ionization, FDCS have been measured as well. Sizeable contributions from purely molecule-specific channels have been identified. The electron spectra reveal the role of the autoionization of the doubly and singly excited states of H2. The latter explicitly involve the coupling between the electronic and the nuclear motion of the molecule. This is a clear manifestation of a breakdown of the Born-Oppenheimer approximation [2].
I. Ben-Itzhak et al., J. Phys. B 29, L21 (1996)
C. Dimopoulou et al., Phys. Rev. Lett., 93, 123203 (2004)