Excited-State Dynamics in Molecular Systems

Excited-state dynamics encompasses the sequence of events that unfold when a molecule absorbs photons and transitions from its electronic ground state to higher-lying excited states. This process is governed by potential energy surfaces and the coupling between electronic and nuclear motion, giving rise to phenomena such as internal conversion, intersystem crossing and non-radiative relaxation. Ultrafast spectroscopic techniques and computational methods based on surface-hopping or wavepacket propagation have revealed that coherent oscillations between electronic and vibrational degrees of freedom often steer the fate of the excited population. In complex organic and biological chromophores, these dynamics determine the efficiency of energy transfer, charge separation and light harvesting. A detailed understanding of non-adiabatic coupling—where electronic states mix due to nuclear motion—permits the rational design of materials for photovoltaics, optoelectronics and photochemical switches. Across chemical systems from conjugated polymers to photosynthetic complexes, excited-state lifetimes range from femtoseconds to microseconds, with both localised and delocalised excitonic states playing key roles in function. By mapping the pathways of ultrafast relaxation and coherent energy flow, researchers can tailor molecular architectures to optimise conversion of light into chemical or electrical energy.

Research from Nature Portfolio

Recent studies have uncovered universal features of coupled electronic-vibrational evolution in conjugated organic materials. Simulations of exciton–vibrational coherence demonstrate that non-adiabatic transitions guided by wavefunction symmetries produce periodic oscillations and maintain phase relationships across ensembles, pointing to design principles for efficient energy transport. In parallel, investigations into chlorophylls have elucidated the side-group dependence of non-radiative relaxation pathways: distinct intramolecular wavefunction migrations and electron–vibrational couplings in chlorophyll A and B determine their sub-picosecond internal conversion times, with direct implications for photoprotection and light-harvesting in natural photosystems.

Excited-State Dynamics in Molecular Systems publication trend

The graph below shows the total number of articles in excited-state dynamics in molecular systems across all publications each year (not limited to Nature Index journals).

Technical terms

Exciton: A quasiparticle comprising a bound electron–hole pair that mediates energy transport within and between molecules.

Non-adiabatic coupling: The interaction between electronic states induced by nuclear motion, enabling radiationless transitions across potential energy surfaces.

Internal conversion: A rapid, non-radiative process by which a molecule dissipates electronic energy to vibrational modes, transitioning between electronic states of the same spin multiplicity.

Coherence: The preservation of fixed phase relationships between quantum states, leading to oscillatory dynamics in combined electronic and nuclear wavefunctions.

Dexter-type energy transfer: A short-range mechanism for triplet energy transfer involving simultaneous exchange of electrons between donor and acceptor molecules.

References

1. Coherent exciton-vibrational dynamics and energy transfer in conjugated organics. Nature Communications (2018).
2. Non-radiative relaxation of photoexcited chlorophylls: theoretical and experimental study. Scientific Reports (2015).
3. Effect of conformational disorder on exciton states of an azobenzene aggregate. Physical Chemistry Chemical Physics (2022).
4. Photoexcited organic molecules en route to highly efficient autoionization. The Journal of Chemical Physics (2020).