We discuss the quantum dynamics of the excitation of a diatomic molecule in the presence of external force fields and the general role of orientation on the manipulation of molecular structure. We review the dynamics of the HF molecule in the presence of a static electric field during and after 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. The coherent motion of rotational wave packets obtained from orientation in a static field is compared with the motion of rotational coherent states. Values are given for static field strengths needed to orient molecules such that their internal dynamics can be described by simplified, purely vibrational models. The results are discussed in comparison with the orientation of adsorbed molecules on metal surfaces. (C) 2004 Wiley Periodicals, Inc.
