Dynamics of collinear A + BC systems

Abstract

A pair of coordinates, one along the minimum reaction path and one normal to it, is employed to treat the collinear dynamics of processes of the type A+B−C→A−B+C. Two potential-energy surfaces are considered: Surface I in which the activated state lies in the approach portion of the reaction coordinate, and Surface II in which it lies in the retreat coordinate. It is shown analytically, in agreement with previous computer calculations, that for Surface I relative translational energy is effective in surmounting the barrier, and that vibration energy is ineffective. For Surface II vibrational energy is effective and relative translational energy ineffective. Consideration is also given to the effects of the relative masses of A, B, and C in determining the energy distribution of the products. Two cases are considered: (1) A light and B and C heavy (L+HH), and (2) A and B heavy and C light (H+HL). It is shown that Case (1) tends to lead to products of high translational and low vibrational energy, whereas Case (2) favors high vibrational energy and low translational energy.