Kinematic effects arising from an intrinsic metric of internal space in structural isomerization dynamics of atomic clusters

Dr. Tomohiro Yanao, Department of Complex Systems Science, Graduate School of Information Science, Nagoya University

Kinematic effects as well as the potential-energy topography can often play predominant role in large-amplitude collective motions of polyatomic molecules. In this talk, I will deal with the structural isomerization dynamics of atomic clusters under zero total angular momentum, and focus on the kinematic effects that originate from an intrinsic non-Euclidean metric of the internal space.

The so-called principal-axis hyperspherical coordinates are introduced to clarify both the mechanism of the isomerization dynamics and associated kinematic effects on the basis of a gauge-theoretical formalism for the separation of rotations and internal motions in many-body systems. A force called democratic centrifugal force arises from an internal motion called kinematic or democratic rotation. This force tends to elongate the system in the direction of one of the principal axes and gives rise to a trapped motion in the vicinity of dividing surfaces of cluster structural change.

I will also talk about a kinematic effect associated with the Eckart frame, which is the most standard body frame in the theory of molecular vibrations. It is shown by a numerical experiment that the gauge field associated with the Eckart frame, which is often disregarded in the normal-mode analysis, has an effect of suppressing the rate of isomerization reaction of clusters to a considerable amount. This suppressing effect is rationalized in terms of the principal-axis hyperspherical coordinates.