Size Evolution of Photoabsorption Spectra of Small Clusters: A Computational Study.

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Atomic and Molecular Physics

Background:

• Understanding the electronic structure and properties of atomic clusters is crucial for various fields.
• Sodium clusters (NaN) exhibit unique properties that change significantly with size.
• Previous studies have explored smaller sodium clusters, but a detailed analysis of the N=5-9 range was needed.

Purpose of the Study:

• To calculate and analyze the photoabsorption spectra of sodium clusters (NaN) for N=5-9.
• To investigate potential structural transformations within these clusters as a function of size.
• To compare computational results with experimental data and previous theoretical calculations.

Main Methods:

• Utilized a diatomics-in-molecules (DIM) like electronic structure model.
• Employed a path-integral Monte Carlo (PIMC) sampling method for spectral calculations.
• Performed detailed comparisons with existing experimental data and theoretical results for NaN (N=3-8).

Main Results:

• Calculated photoabsorption spectra for NaN clusters (N=5-9).
• Observed a qualitative change in the spectra at N=9, signaling a structural transition.
• Interpreted this transition as a shift from trimer-like ionic cores (N≤7) to dimer-like ionic cores (N=9).
• Identified an intermediate state for N=8 with coexisting trimer-like and dimer-like cores.

Conclusions:

• The study confirms a significant structural transformation in sodium clusters around N=9.
• The observed spectral changes are directly linked to the evolution of the ionic core structure.
• Computational results align well with available experimental data, validating the theoretical approach.