A kinetic Monte Carlo study of desorption of H2 from graphite (0001)

TL;DR

This study uses kinetic Monte Carlo simulations to analyze H2 desorption from graphite (0001), successfully reproducing experimental peaks and providing insights into the desorption process relevant to interstellar chemistry.

Contribution

It introduces a simulation approach that accurately models H2 desorption peaks from graphite, incorporating ab-initio derived barriers and matching experimental data.

Findings

Simulations reproduce two main desorption peaks observed experimentally.

An intermediate shoulder peak is explained by the model.

Barriers obtained from ab-initio calculations improve simulation accuracy.

Abstract

The formation of H2 in the interstellar medium proceeds on the surfaces of silicate or carbonaceous particles. To get a deeper insight of its formation on the latter substrate, this letter focuses on H2 desorption from graphite (0001) in Temperature-Programmed-Desorption Monte-Carlo simulations. The results are compared to experimental results which show two main peaks and an intermediate shoulder for high initial coverage. The simulation program includes barriers obtained by ab-initio methods and is further optimised to match two independent experimental observations. The simulations reproduce the two experimental observed desorption peaks. Additionally, a possible origin of the intermediate peak is given.