Darmstadt 2008 – scientific programme

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A: Fachverband Atomphysik

A 17: Collision processes and energy transfer I (jointly with MO)

A 17.1: Invited Talk

Thursday, March 13, 2008, 08:30–09:00, 3F

Reactions of negative ions at low energy — Jochen Mikosch, Sebastian Trippel, Rico Otto, Christoph Eichhorn, Petr Hlavenka, Matthias Weidemüller, and •Roland Wester — Physikalisches Institut, Universität Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg

Interactions of negative ions with small organic molecules represent model systems for the investigation of reaction dynamics in few-body systems. Their corrugated potential energy landscape, originating in long-range attractive and short-range repulsive forces, requires the coupling of different degrees of freedom for reactions to occur. We have adopted two complementary approaches to study anion-molecule reaction dynamics. Using velocity map imaging in combination with crossed beams at low energy we study the differential cross section of negative ion reactions. For nucleophilic substitution reactions we have observed several distinct reaction mechanisms when varying the collision energy [1]. Reaction rate measurements in a 22pole ion trap have revealed unexpected temperature-dependences at low temperatures. These results are relevant for the understanding of the negative ion abundances in interstellar molecular clouds.

[1] J. Mikosch et al., Science (in press)