F-D2 state resolved reactive scattering at 180 and 240 meV collision energies. II. Quasi-classical cross sections. A comparison with the experimental results

USING THE QUASI-CLASSICAL TRAJECTORY METHOD TO STUDY THE F + H2 AND ITS ISOTOPIC VARIANTS: VECTOR CORRELATIONS

The vector correlations between products and reagents for the reactions F + HH → HF + H , F + HD → HF + D and F + HT → HF + T , have been investigated using the quasi-classical trajectory (QCT) method on the Stark-Werner (SW) ab initio potential energy surface. The distribution P(θr) of angle between k′ and j′, the distribution P(ϕr) of dihedral angle denoting k-k′-j′ correlation are calculated. The polarization dependent generalized differential cross sections have also been studied. The evident influence of isotope substitution on the product polarization is revealed. This effect may be derived from the different mass factor of the three reactions and the barrier height of the F + H2 PES.

Comparison of experimental time-of-flight spectra of the HF products from the F+H2 reaction with exact quantum mechanical calculations

High resolution HF product time-of-flight spectra measured for the reactive scattering of F atoms from n-H2(p-H2) molecules at collision energies between 69 and 81 meV are compared with exact coupled-channel quantum mechanical calculations based on the Stark-Werner ab initio ground state potential energy surface. Excellent agreement between the experimental and computed rotational distributions is found for the HF product vibrational states v'=1 and v'=2. For the v'=3 vibrational state the agreement, however, is less satisfactory, especially for the reaction with p-H2. The results for v'=1 and v'=2 confirm that the reaction dynamics for these product states is accurately described by the ground electronic state 1 (2)A' potential energy surface. The deviations for HF(v'=3, j' > or =2) are attributed to an enhancement of the reaction resulting from the 25% fraction of excited ((2)P(12)) fluorine atoms in the reactant beam.

Simulation of the reactive scattering of F+D2 on a model family of potential energy surfaces with various topographies: the correlation approach

The connection between the salient features of the potential energy surface (PES) and the dynamical characteristics of the elementary collision process is studied using a correlation approach based on quasiclassical trajectory simulations. The method is demonstrated for the reaction F + D2 --> D + DF for which the scattering characteristics were calculated on a model family of PES's based on a London-Eyring-Polanyi-Sato-type five-parameter equation. The correlations between the reactive cross section and the vibrational and rotational quantum numbers and the scattering angle of the DF product, and the various parameters of the collinear and noncollinear PES's, such as the location and height of the minimal barrier and the Sato coefficients, are reported. Although usually correlations between two variables suffice, in some cases coefficients of correlation among three variables are required. The role of nonlinear parameter dependencies in computing the correlation coefficients is also considered. The correlation approach makes it possible to examine a large set of potential surfaces without intermediate human control and obtain quantitative information.