Photocyclization of trans-stilbene induced by an ultrafast laser pulse

We predict that photocyclization of trans-stilbene to 4a,4b-dihydrophenanthrene (DHP) can be achieved with a femtosecond-scale laser pulse. Specifically, we have performed dynamical simulations in which the original trans-stilbene molecule is observed first to isomerize to cis-stilbene (as an excited-state intermediate) after more than one picosecond, and then to form a new bond to become DHP, after a few hundred additional femtoseconds. The process is initiated by excitation from the S 0 electronic state to S 1 , with subsequent de-excitation at avoided crossings.