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Published October 22, 2004 | public
Journal Article

Electrons in Finite-Sized Water Cavities: Hydration Dynamics Observed in Real Time


We directly observed the hydration dynamics of an excess electron in the finite-sized water clusters of (H_2O)^-_n with n = 15, 20, 25, 30, and 35. We initiated the solvent motion by exciting the hydrated electron in the cluster. By resolving the binding energy of the excess electron in real time with femtosecond resolution, we captured the ultrafast dynamics of the electron in the presolvated ("wet") and hydrated states and obtained, as a function of cluster size, the subsequent relaxation times. The solvation time (300 femtoseconds) after the internal conversion [140 femtoseconds for (H_2O)^-_35] was similar to that of bulk water, indicating the dominant role of the local water structure in the dynamics of hydration. In contrast, the relaxation in other nuclear coordinates was on a much longer time scale (2 to 10 picoseconds) and depended critically on cluster size.

Additional Information

© 2004 American Association for the Advancement of Science. 16 July 2004; Accepted 25 August 2004; Published online 16 September 2004. We thank M. A. Johnson and K. H. Bowen for helpful communication. Supported by the National Science Foundation.

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