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Ortho-para conversion of interstitial H2 in Si
M Hiller1, E V Lavrov, J Weber
1Technische Universität Dresden, 01062 Dresden, Germany.
Physical Review Letters
|March 16, 2007
Summary
Isolated hydrogen molecules (H2) in silicon undergo ortho-para conversion, driven by interactions with silicon
Area of Science:
- Solid-state physics
- Materials science
- Quantum chemistry
Background:
- Isolated interstitial hydrogen molecules (H2) exist in crystalline silicon.
- Understanding H2 dynamics is crucial for semiconductor properties.
Purpose of the Study:
- To investigate the ortho-para conversion of H2 in single-crystalline silicon.
- To elucidate the mechanism driving this conversion process.
Main Methods:
- Raman scattering spectroscopy was employed to monitor H2.
- Experiments were conducted at cryogenic (77 K) and room (300 K) temperatures.
Main Results:
- Ortho-to-para conversion rate at 77 K is approximately 0.015 h⁻¹.
- Para-to-ortho transition observed at 300 K with a rate of ~0.18 h⁻¹.
- A thermodynamically nonequilibrium ortho-para ratio is established at 300 K.
Conclusions:
- The ortho-para conversion is likely mediated by H2 interaction with the nuclear magnetic moment of 29Si.
- Temperature significantly influences the conversion direction and rate, leading to non-equilibrium states.
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