I-E-1 Nonadiabatic Transition and Chemical Dynamics: Multi-Dimensional Tunneling Theory and Applications of the Zhu-Nakamura Theory

Tunneling and nonadiabatic transition are the most important quantum mechanical effects in chemical dynamics. They are important not only for understanding the dynamics properly, but also for controlling molecular functions. The Zhu-Nakamura (ZN) theory can be combined with the quasi-classical trajectory method and with the IVR (Initial Value Representation)-type semiclassical theory to deal with large chemical systems. Laser control of molecular processes and control of molecular functions can also be realized by properly controlling nonadibatic transitions. Furthermore, we have recently formulated an accurate theory for evaluating tunneling splitting and tunneling decay rate in multi-dimensional systems and also developed an efficient method to find caustics in multi-dimensional space. These methods combined with the ZN theory are expected to clarify various large scale chemical dynamics. This is a short review article on our recent activities mentioned above.