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A: Fachverband Atomphysik

A 12: Interaction of matter with ions I

A 12.1: Hauptvortrag

Dienstag, 15. März 2011, 14:00–14:30, BAR 106

Dissociative charge transfer into molecular ions — •Lothar Ph. H. Schmidt, Reinhard Dörner, and Horst Schmidt-Böcking — Institut für Kernphysik, Goethe-Universität Frankfurt am Main

The dissociative electron transfer from He into slow hydrogen molecular ions was measured in a kinematically complete experiment by using cold target recoil ion momentum spectroscopy (COLTRIMS) in combination with a molecular fragment imaging technique. Neutral molecules produced by electron capture into an excited electronic state dissociate in a second step of the reaction.

We were able to determine the initial vibration energy from the measured momenta. The vibrationally excited states yield a multi peak structure in the measured kinetic energy releases (KER) distribution. We used several models as the reflection approximation to reconstruct the square of the initial nuclear wave functions.

In case of close collisions between the molecule and the helium atom we find a striking two center interference pattern in the He transverse momentum distribution. From that - just as for the case of an optical double slit experiment - we can infer the distance between the scattering centers. We observed a correlation between the interference pattern and the selected KER as expected from the reflection approximation.

Using HD⁺ labels the molecular scattering centers by the isotope mass. This does not lead to a loss of interference fringe contrast, but modifies the interference pattern which can be explained by a breakdown of the axial recoil approximation.