Ultrabroadband 2D electronic spectroscopy with high-speed, shot-to-shot detection

Abstract

Two-dimensional electronic spectroscopy (2DES) is an incisive tool for disentangling excited state energies and dynamics in the condensed phase by directly mapping out the correlation between excitation and emission frequencies as a function of time. Despite its enhanced frequency resolution, the spectral window of detection is limited to the laser bandwidth, which has often hindered the visualization of full electronic energy relaxation pathways spread over the entire visible region. Here, we describe a high-sensitivity, ultrabroadband 2DES apparatus. We report a new combination of a simple and robust setup for increased spectral bandwidth and shot-to-shot detection. We utilize 8-fs supercontinuum pulses generated by gas filamentation spanning the entire visible region (450 -800 nm), which allows for a simultaneous interrogation of electronic transitions over a 200-nm bandwidth, and an all-reflective interferometric delay system with angled nanopositioner stages achieves interferometric precision in coherence time control without introducing wavelength-dependent dispersion to the ultrabroadband spectrum. To address deterioration of detection sensitivity due to the inherent instability of ultrabroadband sources, we introduce a 5-kHz shot-to-shot, dual chopping acquisition scheme by combining a high-speed line-scan camera and two optical choppers to remove scatter contributions from the signal. Comparison of 2D spectra acquired by shot-to-shot detection and averaged detection shows a 15-fold improvement in the signal-to-noise ratio. This is the first direct quantification of detection sensitivity on a filamentation-based ultrabroadband 2DES apparatus.

Engineering couplings for exciton transport using synthetic DNA scaffolds

“…Femtosecond spectroscopy Details of 2D electronic spectroscopy are given in the supplemental information, and the setup is described elsewhere. 101,102 Briefly, 2.8 W of the 5 W output from a 5 kHz Ti:sapphire regenerative amplifier (Coherent Libra) with a 40-fs duration and 800-nm center wavelength was focused into a 1-m tube of argon to generate a broadband continuum. The sub-805-nm portion of the continuum was filtered with a Schott glass filter (Thorlabs FGV9) to provide a center wavelength of 530 nm with a FWHM of 50 nm.…”

Observation of dissipative chlorophyll-to-carotenoid energy transfer in light-harvesting complex II in membrane nanodiscs

“…Ultrabroadband 2DES was employed to determine the impact of the membrane on the photophysical pathways in LHCII. By using a laser spectrum with a significantly broader bandwidth than that in conventional 2DES 46 , we map out energy transfer and dissipation across the broad range of Car and Chl excited states. Supplementary Fig.…”

“…Details of the ultrabroadband 2DES apparatus are provided in the Supplementary Information and in ref. 46 . Glass filters with different cutoff wavelengths were chosen for each dataset in order to tune the spectrum for optimal excitation of the Car S 2 /Chl Q x and Chl Q x /Q y regions, respectively (Supplementary Note 2, Supplementary Fig.…”

Ultrabroadband two-dimensional electronic spectroscopy reveals energy flow pathways in LHCII across the visible spectrum

“…The pulse was compressed with chirped mirrors into 10 fs temporal fwhm, and sent into an allreflective 2DES setup with BOXCARS phase-matching geometry. Additional technical details on the ultrabroadband 2DES apparatus can be found in [3]. The LHCII protein was extracted from spinach and solubilised in 10 mM HEPES, 20 mM NaCl buffer containing 0.03% α-dodecylmaltoside detergent (pH = 7.5).…”