PHYS 334

Femtosecond excitation pulses perturb a molecule's excited state dynamics modulating the process photochemical outcome. Combined with pulse shaping and optimal control, ultrafast pulses provide a tool to arbitrarily modify molecular behavior. Azobenzene is a photochromic molecule with two possible stable isomers. Upon excitation, the molecule evolves in the excited surface in a picosencond time scale. Multiple pathways can lead azobenzene back to the ground state. While one pathway produces isomerization, the other one relaxes the system to its initial isomeric form.

The effect excitation pulse modulation has on the deactivation pathways can be followed by measuring ground state bleach. Any changes observed in the population recovery indicate control over the system dynamics. By varying the phase modulation of the excitation pulse we investigate the excited state dynamics and its role in the isomerization process.