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Updated: Jan 24, 2026

Author Spotlight: Exploring Intrinsically Disordered Protein Dynamics Through NMR Relaxation Experiments
Published on: November 1, 2024
Non-adiabatic molecular dynamics investigation of the size dependence of the electronic relaxation in polyacenes
Evgeny Posenitskiy1, Mathias Rapacioli2, Bruno Lepetit1
1Laboratoire Collisions Agrégats et Réactivité (LCAR), IRSAMC UMR5589, Université de Toulouse (UPS) and CNRS, 118 Route de Narbonne, F-31062 Toulouse, France. posenitskiy@irsamc.ups-tlse.fr.
Abstract:
The Tully's fewest switches surface hopping algorithm is implemented within the framework of the time-dependent density functional based tight binding method (TD-DFTB) to simulate the energy relaxation following absorption of a UV photon by polycyclic aromatic hydrocarbons (PAHs). This approach is used to study the size effect on the ultrafast dynamics in excited states for a special class of PAH species called polyacenes. We determine the dynamical relaxation times and discuss the underlying mechanisms. Our results show that there is a striking alternation in decay times of the brightest singlet state for neutral polyacenes with 3 to 6 aromatic cycles. The alternation corresponds to an order-of-magnitude variation between roughly 10 and 100 fs and is correlated with a qualitatively similar alternation of energy gaps between the brightest state and the state lying just below in energy.
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