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Modelling time-resolved two-dimensional electronic spectroscopy of the primary photoisomerization event in rhodopsin.

  • Author(s): Rivalta, Ivan
  • Nenov, Artur
  • Weingart, Oliver
  • Cerullo, Giulio
  • Garavelli, Marco
  • Mukamel, Shaul
  • et al.

Published Web Location

https://doi.org/10.1021/jp502538m
Abstract

Time-resolved two-dimensional (2D) electronic spectra (ES) tracking the evolution of the excited state manifolds of the retinal chromophore have been simulated along the photoisomerization pathway in bovine rhodopsin, using a state-of-the-art hybrid QM/MM approach based on multiconfigurational methods. Simulations of broadband 2D spectra provide a useful picture of the overall detectable 2D signals from the near-infrared (NIR) to the near-ultraviolet (UV). Evolution of the stimulated emission (SE) and excited state absorption (ESA) 2D signals indicates that the S1 → SN (with N ≥ 2) ESAs feature a substantial blue-shift only after bond inversion and partial rotation along the cis → trans isomerization angle, while the SE rapidly red-shifts during the photoinduced skeletal relaxation of the polyene chain. Different combinations of pulse frequencies are proposed in order to follow the evolution of specific ESA signals. These include a two-color 2DVis/NIR setup especially suited for tracking the evolution of the S1 → S2 transitions that can be used to discriminate between different photochemical mechanisms of retinal photoisomerization as a function of the environment. The reported results are consistent with the available time-resolved pump-probe experimental data, and may be used for the design of more elaborate transient 2D electronic spectroscopy techniques.

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