Nonadiabatic Transitions and Laser Control of Molecular Processes

Nonadiabatic transitions play crucial roles in various dynamic processes in physics, chemistry, and biology. This is true also for laser control of molecular dynamics. In this lecture, I will first explain the importance of nonadiabatic transitions together with the basic theories and then demonstrate how various molecular processes can be controlled by manipulating lasers. Actually, by controlling nonadiabatic transitions among dressed states, we can control various molecular processes. WHAT IS NONADIABATIC TRANSITION? Nonadiabatic transition is a transition between adiabatic states caused by a variation of the adiabatic parameter. This is a highly multi-disciplinary concept, being an origin of the mutability of this world [1]. Potential energy surface crossing is the most typical example, governing various dynamic processes, and is described by the time-independent theory of nonadiabatic transition. On the other hand, transitions induced by external time-dependent fields are treated by the time-dependent theory of nonadiabatic transition. The most basic model was first discussed by Landau, Zener, and Stueckelberg independently in 1932. The Landau-Zener formula or the Landau-ZenerStueckelberg theory is well known. This theory has, unfortunately, many defects and cannot work well in the physically and chemically important regions. After 60 years, we have successfully obtained a complete set of solutions which can be directly applied to practical problems (see the references in [1]). This is called Zhu-Nakamura theory. FLOQUET STATE REPRESENTATION AND NONADIABATIC DYNAMICS Molecular processes in a time-dependent laser field can be described by the following Schroedinger equation: