Metal cluster plasmons analyzed by energy-resolved photoemission

Area of Science:

• Physical Chemistry
• Materials Science
• Nanotechnology

Background:

• The optical properties of metal clusters are crucial for understanding their electronic structure and potential applications.
• Mie theory provides a theoretical framework for the optical response of small particles, but deviations are observed for specific cluster sizes.
• Photoelectron spectroscopy is a powerful technique for probing the electronic states and optical excitations of atomic and molecular systems.

Purpose of the Study:

• To investigate the optical response of size-selected metal clusters, specifically focusing on the plasmon resonance.
• To determine relative photodetachment cross sections and compare different analytical methods for extracting this data.
• To explore the implications of observed optical properties for phenomena like Landau fragmentation.

Main Methods:

• Wavelength-dependent photoemission spectroscopy.
• Energy-resolved photoelectron detection.
• Analysis of relative photodetachment cross sections using different spectral integration methods.

Main Results:

• The plasmon resonance peak for the closed-shell Ag₉₁^- anion was determined to be 3.74 eV.
• This observed peak energy is higher than the small particle limit predicted by Mie theory (3.5 eV).
• Comparison of different methods for extracting cross sections revealed variations in results based on integration strategies.

Conclusions:

• Size-selected metal clusters exhibit optical properties that deviate from classical theories, highlighting quantum size effects.
• The study demonstrates the utility of photoemission spectroscopy for characterizing plasmon resonances in metal clusters.
• The findings open avenues for further research into multielectron excitations and Landau fragmentation in these systems.