Large molecules and their aggregates are core constituents of light accumulating systems of natural and artificial origin. They absorb photons in the spectral region covering most of the solar irradiation spectrum. Later conversion of the excitations into separated charge carriers allow for energy accumulation and storing.
Efficiency of various molecular networks playing is by a large extent determined by the nuclear dynamics, which ranges from coherent nuclear vibrations at high frequencies, to Brownian fluctuations (low frequency thermal vibrations as well as rotations) and up to conformational nuclear dynamics in molecular complexes.
The molecular aggregates have multiple closely lying electronic excited states, whose splittings resonate with nuclear vibrations. The short laser pulses in modern spectroscopy experiments can create superpositions of these electronic states termed by electronic coherences. Electron-vibrational couplings results in mixed types of coherences.
The two dimensional electronic spectra (2DES), is the state of the art spectroscopy approach visualizing superpositions of excited states. The 2DES applied for studies of the exciton dynamics have demonstrated a complex network of the energy transfer pathways as well as long-lasting coherent beats between vibronic states.
We apply theoretical physics and computer modelling approaches based on quantum relaxation theory in describing dynamics and spectroscopy of molecular systems. We evaluate the importance of coherence, entanglement and noise in the energy transport and its efficiency.
The impact of vibrational coherent modes on the 2DES spectra has been first described by our group. We have also devised a robust approach based on oscillation coherence maps to sort origins of the spectral beats. We have also showed how mixing of both, electronic and vibrational, degrees of freedom leads to complicated patterns in the 2DES oscillation maps. Complete perturbation-less treatment of the electron-vibrational coupling showed that most of vibrations become efficiently mixed with electronic transition frequencies and they reshape the 2DES spectra