Surface-hopping trajectories for OH(A(2)Σ(+)) + Kr: extension to the 1A″ state

Area of Science:

• Chemical Physics
• Molecular Dynamics
• Spectroscopy

Background:

• Understanding collisional quenching and energy transfer is crucial for chemical kinetics and atmospheric chemistry.
• Previous theoretical studies of hydroxyl radical (OH) excited states interacting with noble gases had limitations in accuracy.
• Accurate modeling of rotational and Lambda-doublet state populations is essential for interpreting experimental data.

Purpose of the Study:

• To develop an improved theoretical model for rotational energy transfer and collisional quenching of electronically excited OH(A) radicals by Kr.
• To investigate the role of multiple electronic state couplings in non-adiabatic dynamics.
• To enhance the agreement between theoretical predictions and experimental observations.

Main Methods:

• Trajectory surface hopping (TSH) calculations were employed to simulate the dynamics.
• The study included electronic coupling between the 2(2)A' and 1(2)A' states.
• Renner-Teller and Coriolis roto-electronic couplings between the 1(2)A' and 1(2)A″, and 2(2)A' and 1(2)A″ states were incorporated.

Main Results:

• The new multi-state TSH calculations show improved agreement with experimental data compared to simpler two-state models.
• Predictions for OH(X) rotational and Lambda-doublet quantum state populations were notably enhanced.
• Discrepancies persist, suggesting potential issues with potential energy surfaces, couplings, or the classical treatment of non-adiabatic effects.

Conclusions:

• Incorporating a more comprehensive set of couplings significantly improves theoretical predictions for OH(A)-Kr collisions.
• The study highlights the importance of considering multiple electronic states and specific types of couplings (Renner-Teller, Coriolis) for accurate dynamics.
• Further refinements in potential energy surfaces and coupling representations are needed to fully resolve remaining theoretical-experimental discrepancies.