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Mode-specific tunneling using the Qim path: theory and an application to full-dimensional malonaldehyde
1Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA.
The Journal of Chemical Physics
|October 29, 2013
Summary
This study introduces a new theory for mode-specific tunneling, enhancing predictions by analyzing normal mode projections onto a general tunneling path. The theory accurately models tunneling enhancement in malonaldehyde, agreeing with experimental results.
Area of Science:
- Quantum Chemistry
- Chemical Dynamics
- Spectroscopy
Background:
- Understanding tunneling is crucial for chemical reactions.
- Existing theories struggle to accurately predict mode-specific tunneling enhancements.
Purpose of the Study:
- To develop a new theory for mode-specific tunneling.
- To investigate the role of normal mode projections in tunneling.
- To apply the theory to malonaldehyde and compare with experimental data.
Main Methods:
- Utilizing the imaginary-frequency normal mode (Qim) path and relaxed potential (V(Qim)).
- Projecting minimum normal modes onto the Qim path to determine turning points.
- Calculating tunneling changes upon mode excitation.
Main Results:
- The theory accurately predicts tunneling enhancement in malonaldehyde.
- Results show semi-quantitative agreement with experimental data for modes with significant tunneling enhancement.
- Vibrationally adiabatic (VA) theory applicability is clarified, succeeding for modes with zero projection and failing for those with large enhancement.
Conclusions:
- The presented theory provides a robust framework for understanding mode-specific tunneling.
- The projection method offers insights into vibrational effects on tunneling.
- The study validates the limitations of simple VA theory in certain scenarios.
