Quantum surface diffusion of vibrationally excited molecular dimers
1Theory of Condensed Matter, Institute for Molecules and Materials, Radboud University Nijmegen, Toernooiveld 1, 6525ED Nijmegen, The Netherlands.
The Journal of Chemical Physics
|January 11, 2007
Summary
Quantum tunneling in molecular dimers allows for efficient diffusion on surfaces. Resonant states and vibrational mixing enhance tunneling probabilities, crucial for understanding thermal diffusion at the quantum level.
Area of Science:
- Surface science
- Quantum dynamics
- Chemical physics
Background:
- Understanding molecular diffusion on surfaces is key in surface science.
- Classical models struggle to explain quantum phenomena like tunneling.
- Molecular dimers exhibit complex interactions influencing their surface dynamics.
Purpose of the Study:
- Investigate thermally activated quantum diffusion of molecular dimers.
- Analyze the role of potential energy surfaces and vibrational states in tunneling.
- Develop an approximate quantum description of thermal diffusion.
Main Methods:
- Time-dependent wave packet method used for quantum diffusion simulations.
- Analysis of potential energy surfaces from intradimer and dimer-surface interactions.
- Calculation of transmission coefficients to describe diffusion.
Main Results:
- Identified resonant states leading to high tunneling probabilities at specific energies.
- Demonstrated that tunneling induces mixing of vibrational states for soft molecular bonds.
- Defined an effective temperature-dependent activation energy for quantum thermal diffusion.
Conclusions:
- Quantum tunneling significantly impacts molecular dimer diffusion on surfaces.
- Vibrational state and resonant states are critical factors in tunneling efficiency.
- The developed quantum model provides a basis for comparing with classical diffusion.
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