43375-AC6
Theoretical Studies of Coherent Molecular Vibrations in Electronic Energy Transfer
We are investigating the control of electronic energy transfer in molecular dimers through the preparation of specific vibrational coherences prior to electronic excitation. Laser-driven coherent nuclear motion can affect the instantaneous resonance between site-excited electronic states so as to influence short-time electronic excitation transfer (EET). We have proposed nonlinear wave-packet interferometry (nl-WPI) experiments to monitor the electronic and vibrational dynamics in dimer complexes following initial vibrational excitation. The electronic transition moments of the constituent monomers were assumed to have a fixed relative orientation, while the overall orientation of the complex was distributed isotropically. In nl-WPI measurements, two pairs of polarized, phase-related femtosecond pulses generate superpositions of coherent nuclear wave packets in optically accessible electronic states. Interference in the fluorescence signal due to the overlap among the superposed wave packets provides amplitude-level information on the nuclear and electronic dynamics. We derived expressions for the nl-WPI signal following the control pulse (or control-pulse sequence). We included the limiting case of coincident arrival by pulses within each phase-related pair in which nl-WPI reduces to a conventional fluorescence-detected pump-probe experiment, and performed model calculations with Hamiltonian parameters chosen to represent dithia-anthracenophane.
