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Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis
Published on: March 29, 2016
Analysis of molecular hydrogen formation on low-temperature surfaces in temperature programmed desorption experiments
1Physics Department, Syracuse University, Syracuse, New York 13244, USA.
The Journal of Physical Chemistry. A
|November 9, 2007
Summary
Amorphous silicate grains efficiently catalyze molecular hydrogen formation in diffuse interstellar clouds. This process is crucial for astrochemistry, occurring within a specific temperature range of 9–14 K.
Area of Science:
- Astrochemistry
- Surface Science
- Heterogeneous Catalysis
Background:
- Molecular hydrogen (H2) formation on low-temperature surfaces is vital for understanding elementary steps in heterogeneous catalysis and its role in astrochemistry.
- Investigating H2 formation mechanisms on interstellar dust grains is crucial for understanding chemical evolution in space.
Purpose of the Study:
- To experimentally investigate the formation of molecular hydrogen (H2) on amorphous silicate surfaces.
- To determine the energy barriers for H2 formation and evaluate the catalytic efficiency of silicate grains in interstellar clouds.
Main Methods:
- Utilizing temperature-programmed desorption (TPD) to study molecular hydrogen formation.
- Irradiating amorphous silicate surfaces with beams of H and D atoms and monitoring HD molecule desorption rates using mass spectrometry.
- Analyzing experimental data with rate equations to obtain activation energies for diffusion and desorption of H atoms.
Main Results:
- A single-isotope model accurately predicted activation energies for H atom diffusion and desorption.
- Amorphous silicate grains were found to be efficient catalysts for H2 formation at temperatures between 9 and 14 K.
- This temperature range aligns with typical grain temperatures in diffuse interstellar clouds.
Conclusions:
- Amorphous silicate grains are effective catalysts for H2 formation under conditions prevalent in diffuse interstellar clouds.
- The study supports the role of amorphous silicates in facilitating H2 production in the interstellar medium.
- Experimental findings provide quantitative data on H2 formation rates on dust grains, aiding astrochemistry models.
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