H + CD4 abstraction reaction dynamics: product energy partitioning

Area of Science:

• Chemical Dynamics
• Reaction Kinetics
• Quantum Chemistry

Background:

• Understanding product energy distribution is crucial for reaction dynamics.
• The H + CD4 reaction serves as a model system for studying polyatomic reactions.

Purpose of the Study:

• To investigate product energy partitioning in the H + CD4 reaction.
• To compare theoretical models with experimental results for scattering dynamics.

Main Methods:

• Quasi-classical trajectory calculations using B3LYP/6-31G, empirical (EG), and semiempirical (MSINDO) potential energy surfaces.
• Analysis of product translational, vibrational, and rotational energy distributions.
• Comparison of theoretical predictions with experimental data.

Main Results:

• Most energy appears in product translation near the threshold.
• HD vibration and rotation become significant (>20%) above 1 eV collision energy.
• B3LYP/6-31G predicts higher HD vibrational excitation than EG, deviating from Polanyi rules.
• CD3 rotational distribution is largely collision-energy independent (0.75-1.95 eV), favoring excitation about the C2 axis.

Conclusions:

• The B3LYP/6-31G method provides the most accurate description of the H + CD4 reaction dynamics at high collision energies.
• Differences in potential energy surfaces significantly impact product energy partitioning predictions.
• Experimental results align well with B3LYP/6-31G predictions for CD3 rotational excitation.