Origin of power laws for reactions at metal surfaces mediated by hot electrons

TL;DR

This paper presents a model explaining how multiple hot electron excitations induce reactions at metal surfaces, reproducing observed power law behaviors and linking the reaction exponent to vibrational states, with parameters derived from first-principles calculations.

Contribution

It introduces a theoretical model of hot electron-mediated reactions that accurately reproduces experimental power law exponents using parameters from Density Functional Theory.

Findings

The model reproduces the power law dependence of reaction yield on laser fluence.

The exponent n corresponds to the number of vibrational states involved in the reaction.

Parameters are calculated using first-principles methods, enhancing predictive power.

Abstract

A wide range of experiments have established that certain chemical reactions at metal surfaces can be driven by multiple hot electron mediated excitations of adsorbates. A high transient density of hot electrons is obtained by means of femtosecond laser pulses and a characteristic feature of such experiments is the emergence of a power law dependence of the reaction yield on the laser fluence $Y\sim F^n$. We propose a model of multiple inelastic scattering by hot electrons, which reproduces this power law and the experimentally found exponents of several experiments. All parameters are calculated within Density Functional Theory and the Delta Self-Consistent Field method. With a simplified assumption, the power law becomes exact and we obtain a simple and very useful physical interpretation of the exponent $n$, which represents the number of adsorbate vibrational states participating in the reaction.