Line Shape Broadening in Surface Diffusion of Interacting Adsorbates with Quasielastic He Atom Scattering

TL;DR

This paper presents a stochastic model explaining line shape broadening in surface diffusion of adsorbates, highlighting the roles of surface friction and adsorbate interactions, and predicts narrower line shapes at higher coverage under certain conditions.

Contribution

It introduces a stochastic modeling approach that accounts for surface friction and adsorbate interactions using noise sources, offering new insights into line shape broadening phenomena.

Findings

Line shape broadening can be explained by a stochastic model with two noise sources.

Under weak adsorbate-substrate interactions, line shapes narrow with increased coverage.

The model provides an alternative understanding of experimental observations in surface diffusion.

Abstract

The experimental line shape broadening observed in adsorbate diffusion on metal surfaces with increasing coverage is usually related to the nature of the adsorbate-adsorbate interaction. Here we show that this broadening can also be understood in terms of a fully stochastic model just considering two noise sources: (i) a Gaussian white noise accounting for the surface friction, and (ii) a shot noise replacing the physical adsorbate-adsorbate interaction potential. Furthermore, contrary to what could be expected, for relatively weak adsorbate-substrate interactions the opposite effect is predicted: line shapes get narrower with increasing coverage.