Dynamical, time-dependent view of molecular theory
Erik Deumens2005, Theory and Applications of Computational Chemistry
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Abstract
In this paper we present a time-dependent, direct, nonadiabatic theory of molecular processes. We put this approach in contrast to the current theory paradigm of approximate separation of electronic and nuclear dynamics, which proceeds via approximate electronic stationary states and corresponding potential energy surfaces. This established approach in all its variants has provided a basis for qualitative understanding of rate processes and, for systems with few nuclear degrees of freedom, it has produced quantitative data that can be used to guide experiments. In this picture the dynamics of the reacting system takes place on a stationary electronic state potential surface and may under the influence of nonadiabatic coupling terms "jump" to another potential surface the probability of such transitions often viewed as a statistical "surface hopping" [ J. Chem. Phys., 55 (1971) 562] event. The time-dependent, direct, and nonadiabatic theory presented here is fully dynamical in that the evolving state, which describes the simultaneous dynamics of electrons and nuclei of a reacting system [Rev. Mod. Phys., 66(3), (1994) 917] changes in time under the mutual instantaneous forces in a Cartesian laboratory system of coordinates. This approach, which has been applied to reactive collisions involving polyatomic molecules over a large range of energies, proceeds without predetermined potential energy surfaces, uses total molecular wave functions that are parameterized as generalized coherent states, and imposes no constraints on molecular geometries.
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