Probing Photosynthetic Energy and Charge Transfer with Two-Dimensional Electronic Spectroscopy

Abstract

Two-dimensional electronic spectroscopy (2DES) has emerged as a powerful method for elucidating the structure-function relationship in photosynthetic systems. In this Perspective, we discuss features of two-dimensional spectroscopy that make it highly suited to address questions about the underlying electronic structure that guides energy- and charge-transfer processes in light-harvesting materials. We briefly describe a pulse-shaping-based implementation of two-dimensional spectroscopy that is making the method widely accessible to problems spanning frequency regimes from the ultraviolet to the mid-infrared. We illustrate the utility of 2DES in the context of our recent studies of the primary energy-transfer and charge separation events in the photosystem II reaction center, discussing remaining challenges and speculating about exciting future directions for the field of multidimensional spectroscopy.

Comments on the optical lineshape function: Application to transient hole-burned spectra of bacterial reaction centers

“…1,2 Room temperature time-domain measurements, in contrast, while substantially complicated by the broad, relatively featureless, spectral properties of higher temperature systems, offer the essential advantage of allowing for the characterization of samples not only under biological conditions in vitro but even in vivo in living bacterial cells. [3][4][5] To build a complete picture of any physical system, one must of course be able to compare the results obtained using different methods. In connecting time-and frequency-domain spectroscopic measurements, perhaps the most important point of comparison is the phonon spectral density, J(ω), a frequency-domain profile which describes how strongly a given electronic transition couples to the vibrational motions of a pigment or its environment.…”

Two-dimensional electronic spectroscopy based on conventional optics and fast dual chopper data acquisition

“…5 One example of an important process probed by 2D spectroscopy is energy transfer dynamics. [6][7][8][9] Indications of the presence of energy transfer can be gathered with 1D measurements, however it appears in a very intuitive way in 2D spectra and more importantly un-entangled with other processes. 10 Coupling between electronic states and energy transfer are closely related and when there are couplings between transitions they appear quite distinctly in 2D spectra.…”

Two-Dimensional Electronic Spectroscopy Using Incoherent Light: Theoretical Analysis

“…Cross peaks can be signatures of coupling (in several forms) or energy transfer [47,48]. Cross peaks with oscillating amplitudes are most often signatures of intramolecular vibrational modes (vibrational coherence) or strong electronic coupling (electronic coherence) [41,42,[49][50][51][52].…”