Photodecay dynamics of octaethylporphine in the condensed phase explored via resonance Raman spectroscopy and density functional theory calculation

► Ground state OEP with A1 symmetry was excited by 368.9 nm laser and results in a vertical transition to the S8 (By) state in FC region, then it reorganized and relaxed with B2 molecular symmetry. ► The wave packet is then reflected and oscillation between the two side potential in By state. ► The Raman overlap produces the Raman scattering profile. Symmetry considerations require that such an oscillation can occur only for totally symmetric modes. ► Simultaneously, when wave packet approached the intersection of By and Bx states, only the non-total symmetric modes work to alter the shape of the potential energy surface from B2 to B1 symmetry, and then induces the ultrafast IC happens, decaying to the Bx state, produce the A2 vibronic coupling intensities.