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Internal Rotation of Methane Molecules in Large Clusters
Mikhail N Slipchenko1, Hiromichi Hoshina1, Daniil Stolyarov1
1Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States.
The Journal of Physical Chemistry Letters
|December 15, 2015
Summary
Molecular rotation in methane clusters is confined to the surface, unlike in crystals. Quantum effects keep the cluster surface dynamic even at low temperatures.
Area of Science:
- Physical Chemistry
- Condensed Matter Physics
- Spectroscopy
Background:
- Methane exhibits molecular rotation in its crystalline phase.
- Understanding molecular behavior in clusters is crucial for condensed matter physics.
Purpose of the Study:
- To investigate the rotational dynamics of methane molecules within clusters of varying sizes.
- To compare molecular rotation in methane clusters versus crystalline methane.
Main Methods:
- Infrared laser spectroscopy was used to study methane clusters.
- Clusters were formed in Helium droplets at low temperatures (0.38 K).
- Spectra were analyzed in the ν3 vibrational region of methane.
Main Results:
- Well-resolved rotational structure was observed in clusters up to approximately 50 molecules.
- Molecular rotation in clusters is primarily a surface phenomenon.
- Interior molecules in clusters are in an amorphous state with quenched rotation.
Conclusions:
- Methane cluster surfaces remain dynamically fluxional at low temperatures due to quantum effects.
- Low coordination on the cluster surface facilitates molecular rotation.
- This contrasts with the rotation-quenched amorphous interior of the clusters.
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