Trans-to-cis isomerization of stilbene following an ultrafast laser pulse

Dynamical simulations are reported for trans-to-cis photoisomerization of stilbene induced by a femto-second-scale laser pulse. The results imply that the basic mechanism is the simplest imaginable: Electronic excitation by the laser pulse weakens the central C-C bond, and also excites vibrations of this bond. Vibrational energy redistribution then leads to rotation about the bond, resulting in isomerization. Finally, electronic de-excitation near a conical intersection restores the molecule to the electronic ground state. On the other hand, these dynamical simulations demonstrate complexity in the details and reveal supporting roles for other degrees of freedom, such as torsional motion about the vinyl-phenyl side bonds. (C) 2009 Elsevier B. V. All rights reserved.