Towards Accurate Simulation of Two-Dimensional Electronic Spectroscopy

Abstract

We introduce the basic concepts of two-dimensional electronic spectroscopy (2DES) and a general theoretical framework adopted to calculate, from first principles, the nonlinear response of multi-chromophoric systems in realistic environments. Specifically, we focus on UV-active chromophores representing the building blocks of biological systems, from proteins to nucleic acids, describing our progress in developing computational tools and protocols for accurate simulation of their 2DUV spectra. The roadmap for accurate 2DUV spectroscopy simulations is illustrated starting with benchmarking of the excited-state manifold of the chromophoric units in a vacuum, which can be used for building exciton Hamiltonians for large-scale applications or as a reference for first-principles simulations with reduced computational cost, enabling treatment of minimal (still realistic) multi-chromophoric model systems. By adopting a static approximation that neglects dynamic processes such as spectral diffusion and population transfer, we show how 2DUV is able to characterize the ground-state conformational space of dinucleosides and small peptides comprising dimeric chromophoric units (in their native environment) by tracking inter-chromophoric electronic couplings. Recovering the excited-state coherent vibrational dynamics and population transfers, This article is part of the Topical Collection "Multidimensional Time-Resolved Spectroscopy"; edited by Tiago Buckup, Jeremie Leonard.

Molecular spectroscopy of aqueous solutions: a theoretical perspective

“…The latter approaches have the potential to tackle such complex phenomena, and this field undoubtedly provides an exciting avenue for future developments. 7…”

“…These considerations help to explain why the most successful answer to these problems has been found within the realm of focused models: 6,7 there, the focus is always the molecule, which is accurately described in all its degrees of freedom, whereas the solvent is treated at a lower level of sophistication. This partition can be very successful because it focuses on accurately reproducing the solute-solvent interactions, and thus the effect of the solvent on the spectrum, rather than the properties of the solvent itself.…”

Ab Initio Quasiclassical Simulation of Femtosecond Time-Resolved Two-Dimensional Electronic Spectra of Pyrazine

“…Garavelli, Mukamel, Nenov, Rivalta, and co-workers developed an alternative approach for the simulation of electronic 2D spectra of polyatomic molecules which focuses on the ab initio calculation of fixed-nuclei electronic excitations energies and transition dipole moments with multiconfiguration multireference electronic structure methods. These authors developed comprehensive computational protocols which allow the inclusion of the effects of vibrational modes by harmonic-oscillator or Brownian-oscillator line-shape functions as well as the inclusion of solvent effects in the QM/MM approximation. − Ab initio based simulations of 2D spectra were performed for a variety of molecular chromophores, such as phenol, indole, azobenzene, retinal, and nucleobases, − as well as for several dimers or oligomers (see the reviews). , Most of these applications excluded the study of excited-state dynamics by considering either zero waiting time or waiting times in the picosecond range, when excited states can be assumed to be relaxed to their local energy minima. In a few cases, the excited-state dynamics was described by kinetic master equations with empirical parameters.…”

iSPECTRON: A simulation interface for linear and nonlinear spectra with ab‐initio quantum chemistry software

“…A more convenient way to think of the e and f manifolds is in terms of being resonant with the energy of the pump (e manifold, ω eg energies) and probe (f manifold, ω fe energies) pulses. 39,40 Thus, the assignment of states to either manifold is connected to the experimental conditions.…”

“…Thus, states from the f manifold could be considered "spectator states" in the terminology of transient IR spectroscopy. 14,39 Three non vanishing (under the RWA) independent third-order signals can be obtained for the three-level scheme ( Figure 2d In the SOS framework the first-and third-order response functions (Equations (3) and (5)) are expanded in terms of the system eigenstates. R (1) (t 1 ) thus becomes:…”