Dynamics of electron solvation in molecular clusters

Area of Science:

• Physical Chemistry
• Chemical Physics
• Biophysics

Background:

• Solvated electrons, particularly hydrated electrons (e_aq-), are crucial in condensed phase science.
• Understanding electron-solvent interactions is fundamental, yet aspects like e_aq- localization and relaxation mechanisms remain debated.
• Contrasting models exist for hydrated electron structure and excited-state relaxation dynamics.

Purpose of the Study:

• To investigate the time-resolved dynamics of electron solvation using negatively charged clusters.
• To provide complementary insights into the fundamental understanding of hydrated electron behavior and interactions.
• To experimentally probe relaxation mechanisms and timescales of solvated electrons.

Main Methods:

• Utilized time-resolved photoelectron spectroscopy (TRPES), a femtosecond pump-probe technique.
• Studied mass-selected anions, including (H2O)n-, (MeOH)n-, I-(H2O)n, and I-(CH3CN)n.
• Analyzed electronic excitation and subsequent photodetachment at various time delays.

Main Results:

• TRPES on (H2O)n- and (MeOH)n- clusters showed evidence of ultrafast internal conversion.
• Extrapolated p-state lifetimes were 50 fs for bulk water and 150 fs for methanol.
• Experiments on iodide-solvent clusters probed charge-transfer-to-solvent dynamics and solvent response to excess electrons.

Conclusions:

• Results support the nonadiabatic solvation model for hydrated electron relaxation.
• The study provides critical experimental data on electron solvation dynamics in various solvent environments.
• Investigated complex solvation dynamics in confined solvent cavities, particularly for acetonitrile clusters.