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Analysis of Complex Molecules and Their Reactions on Surfaces by Means of Cluster-Induced Desorption/Ionization Mass Spectrometry
Published on: March 1, 2020
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Influence of surface coverage on the chemical desorption process
1LERMA, Université de Cergy Pontoise et Observatoire de Paris, UMR 8112 du CNRS. 5, mail Gay Lussac, 95031 Cergy Pontoise, France.
The Journal of Chemical Physics
|July 10, 2014
Summary
Chemical desorption allows molecules to escape dust grains in cold space. This study reveals chemical desorption efficiencies for oxygen and ozone formation differ significantly and depend on surface coverage.
Area of Science:
- Astrochemistry
- Surface Science
- Physical Chemistry
Background:
- Molecules observed in gas phase in cold astrophysical environments challenge depletion models.
- Chemical desorption, where newly formed molecules desorb from dust grain surfaces, is a proposed solution.
- Key parameters governing chemical desorption efficiency remain poorly understood.
Purpose of the Study:
- To develop a novel procedure for analyzing di-oxygen and ozone formation via chemical desorption.
- To investigate the influence of surface coverage on chemical desorption efficiency.
- To explore physical parameters affecting chemical desorption.
Main Methods:
- Studied O atom adsorption on oxidized graphite surfaces.
- Analyzed the ratio of di-oxygen (O2) and ozone (O3) synthesized.
- Quantified chemical desorption efficiency under varying surface coverages, including pre-adsorbed N2.
Main Results:
- Chemical desorption efficiency differs by an order of magnitude between O+O and O+O2 reaction paths.
- For O+O reaction, efficiency is ~80% at zero coverage, decreasing to near zero at one monolayer.
- Surface coverage significantly impacts O+O chemical desorption, confirmed by N2 co-adsorption experiments.
Conclusions:
- Chemical desorption is a crucial process for gas-phase molecule survival in interstellar environments.
- Surface coverage is a critical factor controlling chemical desorption efficiency.
- Binding energy, enthalpy of formation, and energy transfer are relevant physical parameters for chemical desorption.
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