Chemistry without potential energy surfaces Highly quasi-degenerate electronic states

2 Chemistry without potential energy surfaces Highly quasi-degenerate electronic states 

1 Nonadiabatic dynamical electron theory for chemical reactions 

It turns out through our extensive studies that the electron wavepacket description of chemical reactions offers an interesting and novel way of comprehending chemical phenomena, in which the shift of nuclear configuration induces a qualitative change in the electronic states through nonadiabatic interactions. This situation is typically observed in chemical reactions that are non-concerted reactions or Woodward-Hoffmann symmetry forbidden 

Let us suppose it is possible to treat the nuclear subsystem in a molecule classically and electronic subsystem quantum mechanically. This type of theoretical framework is called a mixed quantum-classical representation. Such a mixed representation can find many applications in science. For instance, a fast mode such as the proton dynamics in a protein should be considered as a quantum subsystem, while the rest of the skeletal structure can be treated as a classical subsystem [3, 484, 485]. It is quite important in this context to establish the correct equations of motion for each of the subsystems and to ask what are their rigorous solutions and how the quantum effects penetrate into the classical subsystems. By studying the quantum-electron and classical-nucleus nonadiabatic dynamics as deeply as possible, we will see how such rigorous solutions, if any, look like qualitatively and quantitatively. This is one of the main aims of this book. 

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