Generation of semiclassical and delocalized vibrational wave packet motion of HF molecules oriented in an external static electric field

The quantum dynamics of the HF molecule is investigated in the presence of a static electric field and coherent infrared radiation. The time dependent dynamics is induced by infrared multiphoton excitation and the time evolution of the rovibrational wave packet is calculated in configuration space. Results are given for static field strengths needed to orient molecules such that their internal dynamics can be described by simplified, purely vibrational models. For highly oriented HF molecules, time intervals of approximate duration of 70 fs occur repeatedly during and after the excitation in which the reduced vibrational wave packet motion is nearly semiclassical (semiclassical windows). The occurrence of these time intervals can be made more regular after the excitation, if the pulse duration is chosen adequately. (C) 2002 American Institute of Physics.