A simple kinetic theory model of reactive collisions of rigid nonspherical molecules

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Abstract
The classical kinetic theory for dilute gases of rigid convex molecules, as developed by Hoffman (1969), is now applied to the calculation on the bimolecular rate coefficient, the energy‐dependent reaction cross section σ R (E), and the orientation‐dependent differential cross section, for general diatom–diatom reactions. Incorporated in the theory are the angular momentum and the convex shape of the colliding molecules, as well as the dependence of the barrier height upon mutual orientation. Several simple collision systems are considered, including that of two reactive ellipsoidal molecules. For atom–diatom scattering, it is found that, in the post‐threshold region (E≳E 0), σ R (E) has quadratic and higher‐order terms in E−E 0 but no linear term. Like σ R , the differential cross section depends sensitively upon the shape of the colliding molecules, as well as upon the angle‐dependent threshold energy. For the near‐spherical case, one obtains simple formulas that display explicitly the dependence of the cross sections and the rate coefficient upon the pair‐anisotropy parameter λ. In the spherical limit (λ=0), the results reduce to those for the steric model of Levine and Bernstein (1984) and of Smith (1982).