Non-Markovian rate theory on a multidimensional reaction surface: Complex interplay between enhanced configuration...

Area of Science:

• Chemical Physics
• Theoretical Chemistry
• Molecular Dynamics

Background:

• Understanding chemical reaction rates is fundamental in chemistry.
• Existing theories often simplify multidimensional systems and friction effects.
• Higher dimensional systems and non-Markovian friction require advanced theoretical treatment.

Purpose of the Study:

• To develop a generalized theory for barrier crossing rates in multidimensional systems.
• To incorporate non-Markovian friction and bilinear coupling into reaction rate theory.
• To provide a more accurate model for complex chemical reactions.

Main Methods:

• Generalization of existing theoretical schemes to higher dimensions.
• Inclusion of non-Markovian friction along reactive and nonreactive coordinates.
• Incorporation of bilinear coupling between modes at the Hamiltonian level.
• Model calculation using Zwanzig-Bixon hydrodynamic theory for frequency-dependent friction.

Main Results:

• The theory recovers known rate expressions under specific conditions.
• Increased dimensionality generally reduces the rate, while memory effects increase it.
• Off-diagonal friction terms are predicted to increase the reaction rate.
• Model calculations show deviations from Langer's theory and 2D transition state theory.

Conclusions:

• The developed theory offers an improved description of barrier crossing rates.
• Non-Markovian friction and multidimensionality significantly impact reaction dynamics.
• The findings have implications for understanding complex molecular processes like isomerization.