We begin our discussion with the S 1 and S 0 population evolutions presented in Fig. (a). Similar to azobenzene and due to the same reasons, the nonadiabatic S 1 evolution starts with a delay. For PSB4, however, the delay is longer, around 50 fs, and the population decay is slower. Namely, the S 1 population of PSB4 halves at about 125 fs, and reaches some 20% of its initial value at 200 fs. Fig. displays the SE signal. It is located around 4 eV (which corresponds to the S 0 -S 1 VEE in Table ) and exhibits pronounced slightly damped oscillations with a period of ∼ 30 fs. After 120 fs, the signal retains oscillatory behavior, but becomes more erratic and does not reveal a specific oscillation frequency. The ESA signal of Fig. (c) shows a qualitatively similar behavior, but consists of two leading components: The upper component oscillating around 3.5 eV is produced by the S 1 -S 4 and S 1 -S 5 transitions, while the lower component oscillating around 1 eV corresponds to the S 1 -S 2 transition (Table ). The ESA signal is governed by the stronger Let us now turn to the GSB signals. The cold GSB signal in Fig. (a) exhibits oscillates around 4.0 eV corresponding to the S 0 -S 1 VEE in Table . Fig. , which shows the Fouriertransformed cold GSB signal defined per Eq. ( ), exhibits three peaks located at 300 cm -1 , 1300 cm -1 and 1700 cm -1 . These frequencies correspond to the vibrational periods of 111 fs, 26 fs, and 20 fs, respectively. They are attributed to the torsion of the C 5 --C 6 bond, the waging of the C-C-H or N-C-H modes, and the stretching motion of the C --C bonds, which are assigned according to Table . The three vibrational modes are responsible for the GSB dynamics in Fig. (a): the second and the third mode produce oscillations while the first one causes a slight increase of the oscillation amplitude around ∼ 100 fs. towards the final products. Since vibrational relaxation and dissipation are not accounted for in simulations, it is quite tricky to estimate the final branching ratio of the products. However, as we discussed previously, the C 5 --C 6 torsional motion is of primarily importance in the wavepacket evolution. We thus tried to divide all trajectories according to the dihedral angle of this bond.