Bound-state dynamics, adiabatic approximation

The adiabatic approximation, which is to be applied to bound-state dynamics, involves the separation of fast and slow motions. However, unlike the original application of the Bom-Oppenheimer approximation,77 in which fast electronic motion is separated from the slower nuclear one, there is no clear separation of time scales for nuclear motions. Nevertheless, there is now ample evidence to show that there are always states, to be termed adiabatic, which are accurately described by an adiabatic approximation.66,69-71 78... 

---