Line shape broadening in surface diffusion of interacting adsorbates with quasielastic he atom scattering

Area of Science:

• Surface science
• Physical chemistry
• Computational physics

Background:

• Adsorbate diffusion on metal surfaces often shows line shape broadening with increased coverage.
• This broadening is typically attributed to adsorbate-adsorbate interactions.

Purpose of the Study:

• To propose a novel stochastic model for adsorbate diffusion line shape broadening.
• To investigate the role of noise sources in adsorbate diffusion dynamics.
• To explore coverage-dependent line shape changes, including narrowing.

Main Methods:

• Development of a fully stochastic model incorporating Gaussian white noise and shot noise.
• Analysis of line shape broadening as a function of adsorbate coverage.
• Simulation of adsorbate diffusion dynamics under varying noise conditions.

Main Results:

• The model successfully explains line shape broadening using surface friction (Gaussian white noise) and adsorbate-adsorbate interactions (shot noise).
• For weak adsorbate-substrate interactions, increasing coverage predicts line shape narrowing, contrary to common expectations.
• The stochastic model provides an alternative framework to understand coverage-dependent diffusion behavior.

Conclusions:

• Line shape broadening in adsorbate diffusion can be explained by stochastic noise sources, including surface friction and effective interaction potentials.
• The study highlights the potential for line shape narrowing with increasing coverage under specific interaction conditions.
• This work offers a new perspective on adsorbate diffusion mechanisms on metal surfaces.