Berlin 2001 – wissenschaftliches Programm
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MO: Molekülphysik
MO 6: Dissociation and other Collision Processes
MO 6.2: Vortrag
Dienstag, 3. April 2001, 16:15–16:30, H1058
Vibrational de-excitation and dissociative recombination of H2+ and D2+ in low energy electron collisons — •S. Krohn1,2, H. Kreckel1, L. Lammich1, M. Lange1, D. Strasser2, D. Schwalm1, R. Wester1, A. Wolf1, and D. Zajfman2 — 1Max-Planck-Institut für Kernphysik, Heidelberg — 2Weizmann Institute of Science, 76100 Rehovot, Israel
Rates of vibrational de-excitation and dissociative recombination in collisions between H2+ and D2+ ions and low-energy electrons (kT < 30 meV) have been studied at the storage ring TSR. These inelastic electron collisions proceed through capture of a free electron in an intermediate doubly excited neutral state. Autoionization of this state recovers the ion, but internal excitation energy may be transferred into kinetic energy of the escaping electron (superelastic collision, SEC); dissociation of the doubly excited neutral state, on the other hand, completes dissociative recombination (DR). Mainly through SEC, vibrational cooling of stored H2+ or D2+ ion beams was observed, leading to cold ion beams (>90% in v=0) in less than 60 s; in contrast to previous storage ring experiments, this cooling is achieved for homonuclear species, where radiative relaxation is inefficient. The vibrational populations were monitored by foil-induced Coulomb explosion imaging; in addition, vibrationally specific contributions to the DR signal were obtained by imaging of the recombination fragments. From the time dependence of the vibrational populations absolute SEC rate coefficients were derived. Combining DR and Coulomb explosion data, also vibrational state specific relative DR rate coefficients were determined. Supported by DIP(BMBF) and GIF.