Perturbation theory phase-space transition states

In section 7.2, we saw that the phase space structures including the nonrecrossing transition state and the reactivity boundaries can be identified easily for harmonic approximation, but the effect of couplings complicates the dynamics and makes the identification of transition state difficult. In this section we introduce a method to elucidate the phase space structures in the existence of coupling. The method is called normal form (NF) theory or canonical perturbation theory (CPT). 

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