Various time domains of external field control

1 Various time domains of external field control 

When the frequency of the external field is compatible with the electronic excitation energy and its duration long compared to the nuclear dynamics, we may regard the individual electronic excitation channels as units and exploit coherent interaction among the channels [65]. 

Intense external fields may be regarded better as modifying the potential surfaces in forming dressed states [460], with the surfaces time evolving in the time scale of the envelope function of the external field the vibrational wavefunctions evolving on the dressed states. 

For pulses of shorter durations, we may regard the results as the formation and time evolution of vibrational wavepackets on (the not dressed) electronic states and exploit the timing of electronic excitation/deexcitation [434], directing the wavepacket s destination [324] or avoiding certain potential energy surface features [281]. Alternately, several wavepackets may be formed and the interference among them exploited for control [306]. 

For dynamics of even shorter durations, when the frequency of the external field is such that the time scale of the oscillation of the field is comparable to the time scale of nuclear dynamics, it may be better to regard the potential surfaces as becoming time-dependent through including the interaction potential within them [355]. The potential surfaces time-evolve not only with the envelope function of the external field but follows the oscillation of the external field itself, enabling dynamic Stark control [404]. 

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