Full-dimensional time-dependent wave packet dynamics of H2 + D2 reaction

Area of Science:

• Chemical Kinetics
• Quantum Dynamics
• Molecular Collisions

Background:

• Understanding reaction dynamics in hydrogen-deuterium systems is crucial for combustion and atmospheric chemistry.
• Investigating competitive reaction pathways like collision-induced dissociation (CID), four-center (4C), and single-exchange (SE) reactions provides fundamental insights.

Purpose of the Study:

• To investigate the dynamics of CID, 4C, and SE reactions in H2 + D2 collisions.
• To elucidate the effects of vibrational and rotational excitation on these reaction probabilities.
• To analyze isotope substitution effects on the reaction efficiencies.

Main Methods:

• Utilizing a time-dependent wave packet approach within a full-dimensional model.
• Computing initial state-selected total reaction probabilities for J=0.
• Employing two realistic global potential energy surfaces: Aguado-Suárez-Paniagua and Boothroyd-Martin-Keogh-Peterson (BMKP).

Main Results:

• Vibrational excitation of hot H2 enhances CID, while excitation of cold D2 inhibits it.
• Rotational excitation of reagents significantly influences reaction probabilities.
• 4C and SE reaction probabilities are at least an order of magnitude lower than CID probabilities.
• CID is most efficient for H2 + D2 and least efficient for H2 + H2.

Conclusions:

• The study highlights the complex interplay between vibrational/rotational states and reaction pathways in H2/D2 collisions.
• CID is the dominant reaction channel under the studied conditions.
• Isotope effects significantly alter the efficiency of CID, 4C, and SE reactions.