Analytic Evaluation of Nonadiabatic Couplings within the Complex Absorbing Potential Equation-of-Motion...

Area of Science:

• Theoretical Chemistry
• Quantum Chemistry
• Computational Chemistry

Background:

• Resonance states are crucial in understanding electron dynamics and chemical reactions.
• Nonadiabatic couplings (NACs) govern transitions between electronic states, influencing reaction pathways and spectroscopic properties.
• The complex absorbing potential equation-of-motion coupled-cluster (CAP-EOM-CC) method provides a framework for studying resonance states.

Purpose of the Study:

• To develop and present the theory for evaluating nonadiabatic couplings (NACs) involving resonance states within the CAP-EOM-CC framework.
• To investigate the behavior and ease of evaluation of NACs between different types of states (bound, resonance, pseudocontinuum).
• To analyze the influence of NACs on the chemical fate and spectroscopic signatures of resonances.

Main Methods:

• Implementation of NAC evaluation within the singles and doubles approximation of the CAP-EOM-CC framework.
• Theoretical treatment of resonance states embedded in the continuum.
• Application to fumaronitrile, studying NACs between bound states, resonances, and pseudocontinuum states.

Main Results:

• The theory successfully evaluates NACs involving resonance states within the CAP-EOM-CC method.
• NACs between bound states and resonance states are found to be nearly independent of the complex absorbing potential (CAP) strength.
• NACs between two resonance states or between a bound state and a pseudocontinuum state are more challenging to evaluate.

Conclusions:

• The developed theory provides a robust method for calculating NACs involving resonance states.
• The distinct behavior of NACs between different state types offers insights into their role in chemical dynamics.
• The findings facilitate the modeling of nonadiabatic transitions affecting the chemical fate and spectroscopy of resonances.