Accurate Time-Dependent Wave Packet Calculations for the O(+) + H2 → OH(+) + H Ion-Molecule Reaction

Area of Science:

• Chemical Physics
• Quantum Dynamics
• Astrochemistry

Background:

• The O(+) + H2 reaction is crucial in interstellar chemistry.
• Understanding its dynamics informs models of chemical evolution in space.

Purpose of the Study:

• To accurately calculate reaction probabilities and cross sections for O(+) + H2.
• To investigate the influence of reactant rovibrational states on reactivity.
• To compare quantum mechanical and quasi-classical trajectory methods.

Main Methods:

• Time-dependent wave packet close-coupling calculations.
• Quantum mechanical and quasi-classical trajectory (QCT) calculations.
• Utilized the potential energy surface (PES) by Martı́nez et al.

Main Results:

• Reaction cross section decays rapidly with collision energy, consistent with the Langevin model.
• Rotational excitation of H2 has a moderate effect on reactivity.
• Vibrational excitation of H2 significantly enhances reactivity at higher collision energies.
• Calculated rate constants show good agreement with experimental data.

Conclusions:

• Quantum calculations provide accurate insights into the O(+) + H2 reaction dynamics.
• The PES topography and reagent velocity coupling explain QCT-observed oscillations absent in quantum calculations.