Ultrafast Fluorescence Depolarization in Conjugated Polymers

We report on large-scale simulations of intrachain exciton dynamics in poly(para-phenylenevinylene). Our theoretical model describes Frenkel coupling to both fast, quantized C–C bond vibrations and slow, classical torsional modes. also incorporate system–bath interactions. The is simulated using the time evolution block decimation method, which avoids failures Ehrenfest approximation describe decoherence processes nonadiabatic interstate conversion. System–bath interactions are modeled quantum trajectories Lindblad jump operators. find that following photoexcitation, mechanical entanglement phonons causes exciton–site decoherence. Next, cause stochastic collapse high-energy delocalized excitons into chromophores. Finally, relaxation additional exciton-density localization. relate these dynamical predicted fluorescence depolarization, extract scales corresponding them, thus interpret observed sub-ps depolarization.