We report two-color two-dimensional Fourier transform electronic spectroscopy obtained using an acousto-optic pulse-shaper in a pump-probe geometry. The two-color setup will facilitate the study of energy transfer between electronic transitions that are widely separated in energy. We demonstrate the method at visible wavelengths on the laser dye LDS750 in acetonitrile. We discuss phase-cycling and polarization schemes to optimize the signal-to-noise ratio in the pump-probe geometry. We also demonstrate that phase-cycling can be used to separate rephasing and nonrephasing signal components.

Two-dimensional decay associated spectra 2C2DES Two-color two-dimensional electronic spectroscopy 2DES Two-dimensional electronic spectroscopy 2DIR Two-dimensional infrared spectroscopy 2PE Two-pulse photon echo BBO Beta-barium borate BChl Bacteriochlorophyll BRC Bacterial reaction center CCD Charge-collecting device CGS Common ground state Chl Chlorophyll CP Cross-peak CS Charge separation DAS Decay associated spectra DMSO Dimethyl sulfoxide DO Diffractive optic DSP Digital signal processor EET Excitation energy transfer ESM Exponential series method ESA Excited state absorption xiv ESE Excited state emission ET Energy transfer FRET Fluorescence resonance energy transfer GSB Ground state bleach LHCII Light-harvesting complex II LN Liquid nitrogen LO Local oscillator NMR Nuclear magnetic resonance NOPA Non-collinear optical parametric amplifier OD Optical density PC Prism compressor PERY N,N'-bis (2,6-dimethylphenyl) perylene-3,4,9,10-tetracarboxylicdiimide Pheo Pheophytin PSI Photosystem I PSII Photosystem II RC D1D2-cyt.b559 reaction center complex SFG Sum frequency generation SHB Spectral hole burning SNR Signal-to-noise ratio SPM Self-phase modulation SVD Singular value decomposition TA Transient absorption TRF Time-resolved fluorescence ZAP-SPIDER Zero additional phase spectral interferometry for direct electric field reconstruction xv ABSTRACT Two-Dimensional Electronic Spectroscopy of the Photosystem II D1D2-cyt.b559

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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.

We develop the theoretical framework for calculating magnetic noise from conducting two-dimensional (2D) materials. We describe how local measurements of this noise can directly probe the wave-vector dependent transport properties of the material over a broad range of length scales, thus providing new insight into a range of correlated phenomena in 2D electronic systems. As an example , we demonstrate how transport in the hydrodynamic regime in an electronic system exhibits a unique signature in the magnetic noise profile that distinguishes it from diffusive and ballistic transport and how it can be used to measure the viscosity of the electronic fluid. We employ a Boltzmann approach in a two-time relaxation-time approximation to compute the conductivity of graphene and quantitatively illustrate these transport regimes and the experimental feasibility of observing them. Next, we discuss signatures of isolated impurities lodged inside the conducting 2D material. The noise near an impurity is found to be suppressed compared to the background by an amount that is directly proportional to the cross-section of electrons/holes scattering off of the impurity. We use these results to outline an experimental proposal to measure the temperature dependent level-shift and line-width of the resonance associated with an Anderson impurity.