Narrow Results

Based on the global three-dimensional adiabatic potential surfaces (PESs) 1²A′, 2²A′, 1²A″ [Boggio-Pasqua et al., Phys Chem Chem Phys2:1693, 2000], the stereo-dynamics of the reaction C + CH → C₂ + H has been investigated by using the quasi-classical trajectories (QCT) method. The four polarization-dependent differential cross sections (PDDCSs) and the angular distributions of P(θ_r), P(ϕ_r), P(θ_r, ϕ_r) have been calculated at the collision energy 0.1 eV on the three PESs, respectively. The calculated results indicate that the distribution of the product C₂ is backward-forward scattering on the 1²A′ and 1²A″ PESs and backward scattering on the 2²A′ PES. The product rotational angular momentum is strongly aligned along the perpendicular direction to the reagent relative velocity k on the three PESs. The orientation of the product C₂ rotational angular momentum tends to point to the positive direction of the y-axis on the 1²A′ PES but the negative direction on the 2²A′ and 1²A″ PESs.

Quasi-classical trajectory (QCT) method is used to study the stereo-dynamics of the title reaction on the ground 1 ¹A′ potential energy surface (PES). Differential cross-sections (DCSs) and alignments of the product rotational angular momentum for the reaction are reported. The influence of collision energy on the product vector properties is also studied in the present work. The distribution of angle between k and j′, P(θ_r), the distribution of dihedral angle denoting k-k′-j′ correlation, P(ϕ_r) ⋅ (2π/σ)(dσ₀₀/dω_t), (2π/σ)(dσ₂₀/dω_t), (2π/σ)(dσ₂₂₊/dω_t) and (2π/σ)(dσ_21-/dω_t) have been calculated in the center of mass frame, respectively.

The quasi-classical trajectory (QCT) method and the 1²A′ potential energy surface (PES) [Boggio-Pasqua et al., Phys Chem Chem Phys2:1693, 2000] have been employed to study the stereo-dynamics of the reaction C + CH (v = 0, j) → C₂ + H at different collision energies over the range of 0.01–0.6 eV and for different rotational quantum number j = 0 - 3. The reactive total cross section with initial revibrational state of v = 0 and j = 0 as a function of collision energy is presented and compared with the quantum mechanics results. The forward-backward asymmetry phenomenon has been found in the angular distribution of the products. The calculated distribution of P(θ_r) indicates a strong product alignment perpendicular to k, but this kind of product alignment is found to be rather insensitive to the collision energy. The calculated distribution of P(ϕ_r) revealed that at low collision energy the products tend to be oriented along the negative direction of the y-axis, while at high collision energy, this product orientation tends to be pointed to the positive direction of the y-axis. Such product orientation tends generally to become stronger with the increase of collision energy. Further, product polarization (i.e. orientation and alignment) becomes weak with high rotational excitation of the reagent CH molecule.

The vector correlations between products and reagents of the N(²D) + D₂ reaction are investigated by employing quasi-classical trajectory (QCT) calculation on the accurate DMBE potential energy surface (PES) of the ²A″ state. Stereo-dynamic quantities, including the four generalized polarization-dependent differential cross-sections (PDDCSs), the angular distribution P(θ_r), the dihedral-angle distribution P(φ_r), as well as the product rotational angular distribution in the polar form of P(θ_r, φ_r), are calculated in the center-of-mass (CM) frame. The results indicate that the product rotational angular momentum j′ not only aligns along the y-axis, but also orients to the negative direction of the y-axis. The isotope effect in the context of chemical stereo-dynamics and influences of different versions of ground-state PESs on vector correlations are shown and discussed.