ISBN 9783843901925

978-3-8439-0192-5, Reihe Physik

Rico Otto
Dynamics of a Microsolvated Ion-Molecule Reaction

144 Seiten, Dissertation Albert-Ludwigs-Universität Freiburg im Breisgau (2011), Softcover, B5

Zusammenfassung / Abstract

The study of microsolvated anions allows us to bridge the gap between two extreme environments: the gas phase with isolated free moving particles on the one side, and the liquid phase where strong interactions with the solvent molecules occur on the other side.

In this thesis we study absolute photodetachment cross sections of microsolvated anions in a cryogenic multipole ion trap. Near threshold we use this technique to detect internal cooling of the trapped clusters. Furthermore we study the reaction dynamics of microsolvated OH-(H2O)n clusters with methyl iodide, using crossed beam ion imaging. To prepare the clusters at well defined internal energies, we combine the crossed beam setup with a multipole trap. Various reaction channels can be observed for different cluster sizes. For a nucleophilic displacement reaction we find that the number of observed reaction mechanisms decreases with increasing ion solvation. Quantum chemical calculations support that this is caused by steric restrictions in the system. For a proton transfer reaction the dynamics change from forward scattering in the unsolvated system to backward scattering in the monosolvated system at high energies. A suppression for solvated products is observed, although they are energetically preferred. This can be understood with an unfavorable rearrangement in an intermediate reaction complex.