Effective collision cross section classical trajectory calculations

The important fact is that the number of collisions Zr increases with temperature. It may be attributed to the effect of attraction forces. They accelerate the molecule motion along the classical trajectories favouring more effective R-T relaxation. This effect becomes relatively weaker with increase of temperature. As a result the effective cross-section decreases monotonically [199], as was predicted for the quantum J-diffusion model in [186] (solid line) but by classical trajectory calculations (dotted and broken lines) as well. At temperatures above 300 K both theoretical approaches are in satisfactory mutual agreement whereas some other approaches used in [224, 225] as well as SCS with attraction forces neglected [191] were shown to have the opposite temperature dependence for Zr [191]. Thus SCS results with a... 

Figure 11. Rotational energy , dependence of the cross section for O + HCl and O + DCl reactions at E uk = 10 kcal/mol. Compared are the results of the classical trajectory calculations ( ) [47], kinematic mass model results which only include the energetic effects of the reactant rotation (o). kinematic mass model results which include rotational effects on the distribution of collisions with the barrier in addition to the rotational energetic effects ( ), and the kinematic mass model results for rotationally unexcited reactants 0 = 0) and the translational kinetic energy increased by the amoimt of (A) [62].

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