Hydrated Electron Dynamics: From Clusters to Bulk

The electronic relaxation dynamics of size-selected (H2O)n–/(D2O)n[25 ≤ n ≤ 50] clusters have been studied with time-resolved photoelectron imaging. The excess electron (\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(e_{c}^{-}\) \end{document}) was excited through the \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(e_{c}^{-}(p){\leftarrow}e_{c}^{-}(s)\) \end{document} transition with an ultrafast laser pulse, with subsequent evolution of the excited state monitored with photodetachment and photoelectron imaging. All clusters exhibited p-state population decay with concomitant s-state repopulation (internal conversion) on time scales ranging from 180 to 130 femtoseconds for (H2O)n– and 400 to 225 femtoseconds for (D2O)n–; the lifetimes decrease with increasing cluster sizes. Our results support the “nonadiabatic relaxation” mechanism for the bulk hydrated electron (\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(e_{aq}^{-}\) \end{document}), which invokes a 50-femtosecond \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(e_{aq}^{-}(p){\rightarrow}e_{aq}^{-}(s^{{\dagger}})\) \end{document} internal conversion lifetime.

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