Effects of An Intrinsic Metric of Molecular Internal Space on Chemical Reaction Dynamics

Kinematic effects arising from a metric and a gauge field in molecular internal space are studied in structural isomerization dynamics of three- and four-atom cluster with zero total angular momentum. The principal-axis hyperspherical coordinates (PAHC) are first employed to clarify both the mechanism of the isomerization reaction and associated kinematic effects. A force called "democratic centrifugal force" is obtained as a significant kinematic factor to dominate the isomerization dynamics. This force has an effect of inducing an asymmetry in mass balance of a system, and thereby brings about trapped motions in the vicinity of the transition states of the clusters coupling with the force arising from potential. We quantify the kinematic effects of a gauge field associated with the choice of Eckart frame, which is often disregarded in the conventional picture for molecular vibrations. Numerical study has revealed that the gauge field has an effect of suppressing the rate of isomerization reaction to a considerable amount. We also show mechanism of this suppressing effect in terms of the PAHC.