HYPERSPHERICAL COORDINATE APPROACH TO ATOM DIATOM CHEMICAL-REACTIONS IN THE SUDDEN AND ADIABATIC APPROXIMATIONS

The methodology and the basic physical idea of the sudden and the adiabatic approximations to deal with atom-diatom chemical reactions are reviewed. Reformulation of these approximations in terms of the collinear-type hyperspherical coordinates is presented together with numerical applications to some reactions systems. Practically useful formulae are derived for the evaluation of reaction cross sections and rate constants. Particular emphasis is placed on the power on the hyperspherical coordinate approach, clarification of the reaction mechanisms, and importance of the potential ridge in a reactive transition. Comparison with classical trajectory calculations clearly reveals quantum mechanical tunneling effects. A new approach to rotational transition in a reaction is also discussed briefly. © 1990.