The Dynamics and Kinetics of Reactive Motion Between Multiple Geometric Conformers.
We develop and use new techniques in the study of nonlinear classical Hamiltonian dynamics to construct a new and highly accurate microscopic theory of reaction rates and population decays, focusing on the dynamics and kinetics of isomerization between multiple conformers. The theory is based upon the discovery that the microscopic classical dynamics of barrier crossing and recrossing is mediated by cylindrical separatrix manifolds in phase space. Transverse maps of these cylinders form closed curves known as Reactive Islands. The implementation of this theory is based upon the strategic placement of one or more transverse maps within each conformer of the isomerizing molecule. We call the arrangement of transverse maps the n-map. An accurate kinetic theory which uses no adjustable parameters is formulated, based upon the flux conservation properties of n-map dynamics, and applied to models of isomerization between two and three conformers modeled in two, three and six degrees of freedom. We further show that cylindrical manifolds exist in all classical models of chemical reactions and mediate the reaction dynamics. This information is used to state a general phase space dynamical condition for all chemical reactions which, when satisfied, is both necessary and sufficient for phase space variational transition state theory to be exact in the classical limit. We present a method useful for modeling molecular systems which undergo internal rotations about axes not rigidly fixed in the molecular frame. The method is used to develop a model of the isomerization of stilbene. We also construct and apply a primitive semiclassical theory of collision induced energy transfer based upon the properties of cylindrical manifolds.
- Pub Date:
- January 1990
- Chemistry: Physical; Physics: Molecular