Bonn 2000 – scientific programme
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MO: Molekülphysik
MO 24: kleine Moleküle
MO 24.4: Talk
Friday, April 7, 2000, 12:00–12:15, HS VI
Electron Induced Vibrational De-Excitation of H2+ — •Sven Krohn1, Zohar Amitay1, Adam Baer1, Lars Knoll2, Michael Lange2, Jacob Levin2, Dirk Schwalm2, Zeev Vager1, Roland Wester2, Andreas Wolf2, and Daniel Zajfman1 — 1Weizmann Institute of Science, 76100 Rehovot — 2Max-Planck-Institut für Kernphysik, Heidelberg
Using foil-induced Coulomb explosion imaging combined with the heavy-ion storage ring technique, the relative populations of the first 6 vibrational levels in a beam of H2+ ions interacting with low kinetic energy electrons have been measured for different storage times at the storage ring TSR located at the MPI für Kernphysik.
The slow electrons interact with the H2+ ions through two main processes: On the one hand dissociative recombination (DR) occurs where the electron is absorbed and the molecule dissociates. Since the DR rate depends strongly on the initial vibrational level, this can selectively deplete specific vibrational levels in the ion beam. On the other hand the electron is subject to superelastic collision (SEC) processes, which also is accompanied by vibrational de-excitation.
We demonstrate that SEC caused by interactions with electrons leads to vibrational cooling of H2+ during storage times of up to 15 s.
Using a rate equation model we show that the theoretically predicted rates for this process are too low by at least an order of magnitude in order to reproduce the observed time dependence of the vibrational population. This work was partly funded by BMBF (DIP project) and GIF.