tends towards values of the reactive coordinates |ϕ| > π 2 . While the S 1 population keeps decreasing until 200 fs, i.e., the end of the simulated dynamics, the trans configuration reaches a maximum at around 180 fs and decreases afterwards. This behavior suggests transfer of density from the trans basins to the cis basin on the S 0 PES without population transfer, since the population of S 1 does not increase after 180 fs. An additional feature that we can observe in the plot of the population of S 1 is that the curve hints towards a stabilization after 200 fs.