Berlin 2001 – wissenschaftliches Programm

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A: Atomphysik

A 12: Posters Thursday (Ion/Atom/Molecule/Surface Scattering)

A 12.24: Poster

Donnerstag, 5. April 2001, 12:30–15:00, AT3

Polarization of N₂-molecules in very slow collisions with Kr⁸⁺-ions — •M. Ehrich¹, U. Werner¹, H.O. Lutz¹, T. Kaneyasu², and K. Okuno² — ¹Fakultät für Physik, Universität Bielefeld, 33501 Bielefeld, Germany — ²Dept. of Physics, Tokyo Metropolitan University, 192-0397 Tokyo, Japan

We studied the dissociation of nitrogen molecules in collisions with Kr⁸⁺-ions in the energy range of 19 eV/u to 171 eV/u. The experimental setup is a combination of a Mini-EBIS, a very compact version of an electron beam ion source, and a detector system consisting of two octopole ion beam guides and an charge state analyzer for the scattered projectiles. With this setup all dissociation channels for diatomic molecules can be analyzed in dependence on the initial energy and charge change of the projectile.

The time-of-flight of both fragment ions was measured in coincidence with the final projectile charge state. The derived collisional momentum-transfer and scattering angle confirm that the final fragment charges strongly depend on the scattering angle.

Additionally we observed an anisotropy of the fragmentation which becomes more distinct at higher ionizations of the target molecule and low collision energies (<50 eV/u). This can be explained by the extended over-barrier model and ab initio calculations which predict a polarization of the target molecule by the slow highly charged projectile.