Ultrafast laser pulse control of exciton dynamics:: A computational study on the FMO complex

Femtosecond laser-pulse-induced spatial localization of excitation energy in the FMO complex is suggested theoretically. Based on the Frenkel exciton model for the bacteriochlorophyll (BChl) Q(y)-excitations, the laser-pulse-driven exciton wave packet motion into a single, spatially localized Q, state is described in detail. First, the manner in which excitation energy relaxation and dephasing, as well as the length and overall intensity of the control pulse, determine the control yield is discussed. In a next step, two-exciton states decaying via exciton-exciton annihilation are included, and a preliminary attempt is undertaken to account for structural and energetic disorder. Although the latter effects may decrease the efficiency of excitation energy localization drastically, it is demonstrated that, even under realistic conditions, tailored laser pulses may deposit energy in a single BChl of the FMO complex.