Berlin 2001 – wissenschaftliches Programm

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A: Atomphysik

A 7: Clusters II: Non-Metal Clusters, Fullerenes, Nanotubes (joint session A and MO)

A 7.5: Vortrag

Dienstag, 3. April 2001, 16:45–17:00, H1012

The phenol-methanol cluster. An interplay between dispersive forces and hydrogen bonding. — •Michael Schmitt and Jochen Küpper — Heinrich-Heine-Universität Düsseldorf, Institut für Physikalische Chemie I, Universitätsstr. 26.43.02

The structure of the hydrogen bonded phenol-methanol cluster will be deduced from results of rotationally resolved laser induced fluorescence. This technique enables to discriminate between different clusters by the species specific absorption of a chromophor incorporated in the cluster. Furthermore it is possible to determine rotational and centrifugal distortion constants in the electronic ground and excited state. Geometry changes upon electronic excitation which are due to changes in the electronic structure are investigated. The internal motion of the methyl group in the methanol moiety can be employed for an investigation of the perturbation of the rovibronic spectrum, which yields additional structural information. It will be shown that the structure of the hydrogen bond in this cluster deviates considerably from the trans-linear structure in phenol-water. This can be explained by an additional dispersive interaction between the aromatic π-system and the methyl group. Ab initio calculations at MP2 level seem to overestimate the dispersion in the present case, but nevertheless give quite reliable values for the rotational constants. In the electronically excited state, the methyl group is bent considerably more towards the aromatic ring compared to the electronic ground state, indicating an increased dispersive interaction.