Coupled 3D (J ≥ 0) Time-Dependent Wave Packet Calculation for the F + H₂ Reaction on Accurate Ab Initio Multi-State...

Area of Science:

• Quantum Chemistry
• Chemical Dynamics
• Theoretical Spectroscopy

Background:

• Accurate potential energy surfaces (PESs) are crucial for understanding chemical reaction dynamics.
• Nonadiabatic and spin-orbit (SO) couplings significantly influence reaction pathways, especially in systems with multiple electronic states.

Purpose of the Study:

• To compute adiabatic and diabatic potential energy surfaces (PESs) and nonadiabatic/SO coupling terms for the F + H2 system.
• To investigate the impact of nonadiabatic and SO effects on the integral cross sections (ICSs) and rate constants.
• To validate the accuracy of the calculated diabatic PESs through scattering calculations.

Main Methods:

• Multireference configuration interaction (MRCI) level of theory for calculating electronic states and coupling terms.
• Adiabatic-to-diabatic transformation to formulate the diabatic Hamiltonian matrix.
• Coupled 3D time-dependent wave packet formalism to perform scattering calculations, considering total angular momentum and helicity quantum numbers.

Main Results:

• Calculated adiabatic PESs, nonadiabatic, and SO coupling terms for the lowest three electronic states of F + H2.
• Computed integral cross sections (ICSs) and rate constants, showing convergence profiles of reaction probabilities.
• Comparison of calculated ICSs and rate coefficients with existing theoretical and experimental data.

Conclusions:

• The study provides accurate diabatic PESs and coupling terms for the F + H2 system.
• Nonadiabatic and SO effects play a significant role in the reaction dynamics.
• The results offer a benchmark for future theoretical and experimental investigations of this important reaction.