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 (H2O)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 (H2O)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.
Paik
D Hern
DH
Arthur Amos Noyes Laboratory of Chemical Physics, Laboratory for Molecular Sciences, California Institute of Technology, Pasadena, CA 91125, USA.
Lee
I-Ren
IR
Yang
Ding-Shyue
DS
Baskin
J Spencer
JS
Zewail
Ahmed H
AH