Electron localization in negatively charged formamide clusters studied by photodetachment spectroscopy

Area of Science:

• Physical Chemistry
• Chemical Physics
• Spectroscopy

Background:

• Electron localization in molecular clusters is crucial for understanding solvation dynamics.
• Formamide clusters (FAn-) provide a model system for studying solvent effects on electron behavior.

Purpose of the Study:

• Investigate size-dependent electron localization in negatively charged formamide clusters (FAn-, n=5-21).
• Differentiate between solvated electron states and covalent anion states.
• Analyze the influence of cluster size on electron binding energies and spectral features.

Main Methods:

• Photodetachment spectroscopy was employed to probe electron binding energies.
• Photoelectron spectra were analyzed for various cluster sizes (n=5-21).
• Relative photodetachment cross-section measurements in the near-infrared region were used to assign spectral bands.

Main Results:

• Two distinct bands were observed in the photoelectron spectra, corresponding to different anion isomers.
• A low binding energy band (~1 eV) was assigned to the solvated electron state, indicating initial electron trapping.
• A higher energy band, attributed to the covalent anion state, showed a rapid increase in binding energy with cluster size.
• A unique, remarkable intensity of the higher energy band was observed specifically for n=9.

Conclusions:

• Nascent electron trapping in formamide clusters is primarily governed by the formation of solvated electrons.
• The transition to covalent anion states occurs with significant cluster relaxation and is strongly size-dependent.
• The anomalous band intensity at n=9 suggests a unique structural or electronic configuration in this specific cluster size.