Adiabatic electronic state populations were computed as fractions of trajectories being in the state of interest. The quantum yield Φ was computed as the ratio of the number of the reactive trajectories (i.e., those undergoing trans → cis isomerization) to the number N t of trajectories that reached the ground state within 10 ps. The standard error was calculated as the standard deviation of the sample proportion, ∆Φ = Φ(1 -Φ)/N t . The reactive trajectories were identified monitoring the change in the CNNC dihedral angles from