FEEDBACK QUANTUM CONTROL OF MOLECULAR ELECTRONIC POPULATION TRANSFER

Feedback quantum control, where the sample 'teaches' a computer-contro lled arbitrary lightform generator to find the optimal light field, is experimentally demonstrated for a molecular system. Femtosecond pulse s tailored by a computer-controlled acousto-optic pulse shaper excite fluorescence from laser dye molecules in solution. Fluorescence and la ser power are monitored, and the computer uses the experimental data a nd a genetic algorithm to optimize population transfer from ground to first excited state. Both efficiency (the ratio of excited state popul ation to laser energy) and effectiveness (total excited state populati on) are optimized. Potential use as an 'automated theory tester' is di scussed. (C) 1997 Elsevier Science B.V.