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MO: Molekülphysik
MO 6: Cluster I
MO 6.8: Talk
Monday, March 22, 2004, 15:45–16:00, HS 332
Ab Initio Studies on Size-Dependent H2 Elimination Reaction in Al+(H2O)n — •Chi-Kit Siu — Physikalische Chemie II, Technische Universität München, Lichtenbergstr. 4, D-85748 Garching
Chemical properties of ions in solution are strongly influenced by their solvation environment. Knowledge of the ionic solvation is important for chemical processes in solution, in the atmosphere, and also in biological systems. In order to have better understanding on the ionic solvation, one should pay attention to the vicinity of an ion. However, study on such microscopic solvation is challenging due to the complexity of the solvation structure. A gas phase cluster ion provides a simplified nano-scale model for investigating the structure and the reactivity of a solvated ion. The solvation effects can be monitored via a stepwise solvation by carefully controlling the cluster size in a mass spectrometer. Interestingly, size-dependent intracluster reactions are observed. Al+(H2O)n is one of the typical examples showing such size-dependent effect. A H2 molecule is evaporated out from the clusters at certain sizes. The role of the isomers of Al+(H2O)n for the H2 elimination reaction have been investigated by ab initio calculations. Since the cluster ions are fluxional due to the presence of many hydrogen bonds, knowledge on the relative stability of the stationary structures from conventional quantum chemical calculation is insufficient. The solvation dynamics and the reaction mechanism can be effectively studied by direct sampling of the potential energy surface at finite temperature using Ab Initio Molecular Dynamics method.