Coherent control of the molecular four-wave-mixing response by phase and amplitude shaped pulses

Femtosecond pulse shaping using a spatial light modulator and degenerate fo ur-wave mixing (DFWM) spectroscopy have been combined to control the vibrat ional wave packet motion in the electronic ground and excited states of the prototype molecule K: and, thus, study the influence of phase and amplitud e modulated pulses on the molecular FWM response. It is shown that the vibr ational motion of the potassium dimer is sensitive to the temporal interpul se separation and the adjusted phase differences. A simple theoretical mode l for such arbitrary shaped pulse excitation in a FWM process has been deve loped, which proves to be in excellent agreement with the observed FWM sign al. In addition, the spectrally resolved DFWM signal works as a molecular F ROG providing information about the activated molecular vibrations, the DFW M signal itself and the shapes of the pulses used in the excitation sequenc e. Further more, the experiment was ideal to test the robustness of the evo lutionary algorithm previously used to find new control processes. (C) 2001 Elsevier Science B.V. All rights reserved.