We wanted to investigate more in-depth the differences between the CASPT2 and CASSCF PESs and their coupling, leading to such different time evolution. For this reason, we first computed the static scans along the two coordinates leading to the two degeneracy points (Figure ). We linearly interpolated between the ground state optimized geometry and the CoIns optimized at CASSCF level. The two coordinates sampled in the two scans are the ones that represent the coordinate promoting the reflection (CoIn sloped , Figure ) and the full decay (CoIn peaked , Figure ) to the ground state. The sloped CoIn is mainly characterized by an elongation of the C=CH 2 bond, while the peaked CoIn occurs at a 90 • torsion of the CH 2 group. However, it should be stressed that both these CoIns are minimum energy CoIns and might not be representative of their full seams of CoIns. CASSCF overestimates S 1 energies at the FC point and along both coordinates and the wavepacket, initialized with the same momentum, would approach much slower the two intersections. Already by looking at the scans, we could anticipate different dynamics along the CASPT2 surfaces. Along the reaction coordinate leading to the sloped CI, we can observe all the CASPT2 minima of S 1 far from the intersection between the two surfaces, with respect to the minimum at the CASSCF level. This could lead to a slower deactivation, as well as the very sloped profile after the CoIns, could indicate a strong reflection after the wavepacket crosses it. In the other reaction coordinate, we cannot observe a crossing point located around the CASSCF CoIn, at any of the CASPT2 levels, which could lead to closing this deactivation channel at this level of theory.