Inelastic collision dynamics transfer

McCormack, J. and McCaffery, A.J. (1980). Collision dynamics of excited NaK. II. Rotationally inelastic energy transfer, Chem. Phys., 51, 405-416. 

Gas-phase electron-transfer reactions have been studied using all the experimental methods which are of common use in the reaction dynamics community. These methods have been extensively described in the literature, and it is not necessary to describe them again in detail. We just need to recall a few points, which are necessary to understand the origin of the results discussed in the remainder of the chapter, and only the most recent and comprehensive reviews and a few original papers describing the principal techniques are referred to hereafter. It must be mentioned that the techniques used to study reactive collisions are in very wide use and have also been used to investigate non-reactive collisions, both inelastic and elastic. 

Besides the distance between the nuclear centers, R, the mass transfer, a = A — A2)/ A + A2) and dynamic deformations of nuclear surfaces, fi, play a most important role in fusion-fission and deep inelastic processes of low energy heavy-ion collisions. The corresponding multi-dimensional adiabatic potential energy surface was calculated here within the semi-empirical two-core approach [68] based... 

These definitions are not quite universal. Collisions in which the internal state of one or both collision partners changes are sometimes considered inelastic even if the total internal energy is unchanged, so that there is no change in relative kinetic energy. Collisions in which the possibility of atom transfer needs to be taken into account in the dynamics are often considered reactive, even if the final products are indistinguishable from the reactants. 

The dynamics of the hard-core, square-well problem is particularly simple for the initial conditions just considered. Sometimes multiple collisions occur as shown in Fig. 10.6a. The representative particle collides with wall 1 more than once, i.e., A hits B, then B hits C, and finally B and A collide again before atom and diatom separate. If, as in Fig. 10.6a, BC is initially vibrationless, multiple collisions can only occur when < 60° as ms decreases these become more common and are predominant if < 50°. Such repeated collisions significantly increase the energy transfer instead of (10.7) the inelasticity is... 

Molecular dynamics in its purist approach tries to seek out (and understand) the truly elementary events. Thus it is more interested in the left than in the right panels of Figure 1.2. It is, however, concerned not only with the primary reactive collision process but also with the subsequent non-reactive, inelastic energy-transfer steps that take the system from the nascent distribution of products to the fully relaxed one. The Cl + HI system is not exceptional. Many exoergic reactions release a substantial part of their energy into internal modes of product excitation." A key problem facing us is to understand this observation in terms of the forces that act during the collision. In this introductory case study we use a model. 

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