Düsseldorf 2007 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
SYMC: Symposium Molecular Collisions at ultracold temperatures
SYMC 2: Molecular collisions at ultracold temperatures II
SYMC 2.2: Hauptvortrag
Montag, 19. März 2007, 17:00–17:30, 5D
Cool anion molecule collisions — •Jochen Mikosch, Sebastian Trippel, Rico Otto, Christoph Eichhorn, Matthias Weidemüller, and Roland Wester — Physikalisches Institut, Universität Freiburg
Collisions of neutral molecules with anions at low relative energy are strongly affected by long range ion-dipole interactions. On the potential energy surface reactions are steered through deeply bound entrance and exit channel complexes separated by a central barrier. We investigate the quantum dynamics of reactive collisions, in particular rovibrational state dependencies, tunneling, and stereodynamical effects.
For the SN2 reaction Cl− + CH3Cl we were able to stabilize the short lived collision complex in a high order multipole trap by a third impacting particle. The three body association is strongly enhanced for decreasing temperature. On the other hand the proton transfer of H2 to NH2− exhibits a maximal rate coefficient at around 20 K and is strongly suppressed for decreasing temperature. We also investigate slow collisions of anions with cold neutrals at fixed energy rather than temperature. Crossed beam ion imaging gives access to the doubly differential cross section. A detailed study of the SN2 reaction Cl− + CH3I —→ ClCH3 + I− shows the cone of acceptance opening up for increasing collision energy accompanied by excitation of many vibrational quanta in the molecular product.
We will extend our studies to the stereodynamics of ion-molecule reactions using microsolvated anions, which are subject to stereodynamics hindrance, and alignment in strong laser fields.