Electronic excitation energies, three-state intersections, and photodissociation mechanisms of benzaldehyde and acetophenone

► S1/T2/T1 three-state intersection region in both C6H5CHO and C6H5COCH3. ► Efficient S1/T1 intersystem to T1 via the T2 state as a relay. ► On the T1 state, different bond-fission scenarios.