Accurate diabatic potential energy model for NO3 including spin-orbit coupling.

Area of Science:

• Quantum Chemistry
• Molecular Spectroscopy
• Theoretical Chemistry

Background:

• Spin-orbit (SO) coupling significantly impacts molecular quantum dynamics and spectroscopy.
• Accurate diabatic models for SO coupling, especially when combined with vibronic coupling, are scarce.
• The nitrate radical (NO3) presents a unique challenge due to delocalized SO coupling effects.

Purpose of the Study:

• To develop a comprehensive, geometry-dependent diabatic model for spin-orbit and vibronic couplings in the nitrate radical (NO3).
• To analyze the atomic nature and geometry dependence of SO coupling in NO3.
• To validate the model against existing experimental data for NO3.

Main Methods:

• Development of a fully geometry-dependent diabatic spin-orbit and vibronic coupling model for NO3, building upon a pre-existing diabatic potential energy model.
• Establishment of a semi-quantitative model linking SO coupling to its atomic origins.
• Detailed analysis of the geometry dependence of SO coupling concerning various nuclear motions.

Main Results:

• A novel, geometry-dependent diabatic SO and vibronic coupling model for NO3 was successfully developed.
• The study established a clear link between SO coupling and atomic contributions, revealing its distributed nature in NO3.
• The model's predictions demonstrated excellent agreement with previously reported experimental observations of SO coupling effects in NO3.

Conclusions:

• The developed model provides an accurate theoretical treatment for spin-orbit and vibronic couplings in NO3.
• Understanding the geometry dependence of SO coupling is essential for accurate molecular dynamics and spectroscopy.
• This work advances the study of SO coupling in systems where it is not localized on a single atom.