Ultrafast coherent dynamics of nonadiabatically coupled quasi-degenerate excited states in molecules: Population and vibrational coherence transfers

► A nonadiabatic theory of quasi-degenerate π-electronic states in aromatic molecules. ► Quantum interferences between the nonadiabatically-coupled π-electronic states. ► Analysis of time-dependent vibrational coherence transfer via nonadiabatic couplings.