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Updated: Jul 29, 2026
10:37
Spatial Separation of Molecular Conformers and Clusters
Published on: January 9, 2014
Hydrated electron dynamics: from clusters to bulk
A E Bragg1, J R R Verlet, A Kammrath
1Department of Chemistry, University of California, Berkeley, CA 94720, USA.
Science (New York, N.Y.)
|September 18, 2004
Summary
Size-selected water clusters reveal electronic relaxation dynamics. Ultrafast laser pulses show electron (ec-) excited states decay and repopulate, supporting the nonadiabatic relaxation mechanism for hydrated electrons (eaq-).
Area of Science:
- Physical Chemistry
- Chemical Physics
- Femtochemistry
Background:
- The behavior of excess electrons in water is crucial for understanding various chemical and biological processes.
- Hydrated electrons (eaq-) are fundamental species in aqueous solutions, influencing reactions and biological systems.
- Previous studies suggest complex relaxation dynamics for excess electrons in water clusters.
Purpose of the Study:
- To investigate the electronic relaxation dynamics of size-selected water clusters, specifically (H2O)n- and (D2O)n-.
- To elucidate the mechanism of internal conversion between excited electronic states of excess electrons in water clusters.
- To provide experimental support for the nonadiabatic relaxation mechanism of the bulk hydrated electron (eaq-).
Main Methods:
- Time-resolved photoelectron imaging was employed to study the electronic relaxation dynamics.
- Size-selected (H2O)n-/(D2O)n- clusters (25 <= n <= 50) were used as the experimental system.
- An ultrafast laser pulse excited the excess electron (ec-) from its s-state to a p-state (ec-(p)<--ec-(s)), and subsequent evolution was monitored.
Main Results:
- All studied water clusters exhibited decay of the p-state population with simultaneous repopulation of the s-state (internal conversion).
- The internal conversion lifetimes ranged from 180 to 130 femtoseconds for (H2O)n- and 400 to 225 femtoseconds for (D2O)n-.
- Lifetimes were observed to decrease with increasing cluster size, indicating size-dependent relaxation dynamics.
Conclusions:
- The experimental results support the "nonadiabatic relaxation" mechanism proposed for the bulk hydrated electron (eaq-).
- This mechanism involves an internal conversion lifetime of approximately 50 femtoseconds for the hydrated electron's p-state to a relaxed state (eaq-(p)-->eaq-(s(dagger))).
- The study highlights the importance of cluster size in governing the electronic relaxation pathways of excess electrons in water.
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