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Compaction of microporous amorphous solid water by ion irradiation
U Raut1, B D Teolis, M J Loeffler
1Laboratory of Atomic and Surface Physics (LASP), University of Virginia, Charlottesville, Virginia 22904, USA.
The Journal of Chemical Physics
|July 7, 2007
Summary
Energetic ion irradiation compacts amorphous solid water ice, reducing pore surface area before pore volume. This explains the lack of dangling bonds in interstellar ice, impacting cosmic dust models.
Area of Science:
- Astrochemistry
- Materials Science
- Physical Chemistry
Background:
- Interstellar ices are crucial for molecule formation and dust grain evolution.
- Understanding ice compaction under irradiation is key to interpreting astronomical observations.
Purpose of the Study:
- To investigate the structural changes in amorphous solid water ice upon energetic ion bombardment.
- To correlate changes in porosity with specific spectral features.
Main Methods:
- Vapor-deposited amorphous solid water ice studied at 40 K.
- Characterization using ultraviolet-visible spectroscopy, infrared spectroscopy, and methane adsorption/desorption.
- Analysis of pore volume and internal surface area changes.
Main Results:
- Infrared spectroscopy revealed a decrease in dangling bonds (indicating reduced surface area) preceding pore volume reduction.
- Ultraviolet-visible spectroscopy and methane adsorption/desorption confirmed compaction.
- The observed compaction mechanism provides insights into interstellar ice mantle evolution.
Conclusions:
- Energetic ion impacts compact interstellar icy mantles.
- The observed compaction sequence explains the absence of dangling bond features in molecular cloud infrared spectra.
- This study refines models of interstellar dust and ice processing.
