Spectroscopic signatures of vibronic coherence in artificial dimers: evidence for quantum energy transfer?

by Dr Elisabetta Collini (Dipartimento di Scienze Chimiche, Università di Padova)

Wednesday 28 May 2014, 16:30 → 18:00 Europe/Rome

Aula A. Rostagni (INFN - Padova)

One of the most surprising and significant advances in the study of the photosynthetic light-harvesting process is the discovery that the electronic energy transfer might involve long-lived electronic coherences, also at physiologically relevant conditions. This means that the transfer of energy among different chromophores does not follow the expected classical incoherent hopping mechanism, but that quantum-mechanical laws can steer the migration of energy. The implications of such quantum transport regime, although currently under debate, might have a tremendous impact in our way to think about natural and artificial light-harvesting. Central to these discoveries has been the development of new ultrafast spectroscopic techniques, in particular two-dimensional electronic spectroscopy, which is now the primary tool to obtain clear and definitive experimental proof of such effects. In this seminar I will present the early time dynamics of energy migration in a homo-dimer of a quadrupolar chromophore characterized by 2D electronic spectroscopy, treated as model system of more sophisticated natural and artificial light-harvesting complexes. In agreement with recent theoretical predictions, the obtained results suggest the presence of strong interactions between electronic and vibrational degrees of freedom leading to a rich oscillatory pattern of vibronic coherences, not present in the single monomeric units. The possible connection between such experimentally detected coherences and quantum regime of energy transport will be discussed.