The role of quantum coherence in photochemical functions of molecular systems such as photosynthetic complexes is a broadly debated topic. Coexistence and intermixing of electronic and vibrational coherences has been proposed to be responsible for the observed long-lived coherences and high energy transfer efficiency. However, clear experimental evidence of coherences with different origins operating at the same time has been elusive. In this work, multidimensional spectra obtained from a six-porphyrin nanoring system are analyzed in detail with support from theoretical modeling. We uncover a great diversity of separable electronic, vibrational, and mixed coherences and show their cooperation in shaping the spectroscopic response. The results permit direct assignment of electronic and vibronic states and characterization of the excitation dynamics. The clear disentanglement of coherences in molecules with extended π-conjugation opens up new avenues for exploring coherent phenomena and understanding their importance for the function of complex systems.

V. Butkus, J. Alster, E. Bašinskaitė, R. Augulis, P. Neuhaus, L. Valkunas, H.L. Anderson, D. Abramavicius, D. Zigmantas, Discrimination of Diverse Coherences Allows Identification of Electronic Transitions of a Molecular Nanoring, J. Phys. Chem. Lett., 8(10), 2344–2349 (2017).