| 1. |
- Alster, Jan, et al.
(författare)
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2D Spectroscopy Study of Water-Soluble Chlorophyll-Binding Protein from Lepidium virginicum
- 2014
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Ingår i: The Journal of Physical Chemistry Part B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 118:13, s. 3524-3531
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Tidskriftsartikel (refereegranskat)abstract
- Water-soluble chlorophyll-binding proteins (WSCPs) are interesting model systems for the study of pigment-pigment and pigment-protein interactions. While class IIa WSCP has been extensively studied by spectroscopic and theoretical methods, a comprehensive spectroscopic study of class IIb WSCP was lacking so far despite the fact that its structure was determined by X-ray crystallography. In this paper, results of two-dimensional electronic spectroscopy applied to the class IIb WSCP from Lepidium virginicum are presented. Global analysis of 2D data allowed determination of energy levels and excitation energy transfer pathways in the system. Some additional pathways, not present in class IIa WSCP, were observed. The data were interpreted in terms of a model comprising two interacting chlorophyll dimers. In addition, oscillatory signals were observed and identified as coherent beatings of vibrational origin.
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| 2. |
- Amarotti, Edoardo, et al.
(författare)
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Direct Visualization of Confinement and Many-Body Correlation Effects in 2D Spectroscopy of Quantum Dots
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Ingår i: Advanced Optical Materials. - 2195-1071.
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Tidskriftsartikel (refereegranskat)abstract
- The size tunable color of colloidal semiconductor quantum dots (QDs) is probably the most elegant illustration of the quantum confinement effect. As explained by the simple “particle-in-a-box” model, the transition energies between the levels increase when the “box” becomes smaller. To investigate quantum confinement effects, typically a well-defined narrow size distribution of the nanoparticles is needed. In this contribution, how coherent electronic two-dimensional spectroscopy (2DES) can directly visualize the quantum size effect in a sample with broad size distribution of QDs is demonstrated. The method is based on two features of the 2DES – the ability to resolve inhomogeneous broadening and the capability to reveal correlations between the states. In QD samples, inhomogeneous spectral broadening is mainly caused by the size distribution and leads to elongated diagonal peaks of the spectra. Since the cross peaks correlate the energies of two states, they allow drawing conclusions about the size dependence of the corresponding states. It is also found that the biexciton binding energy changes between 3 and 8 meV with the QD size. Remarkably, the size dependence is non-monotonic with a clear minimum.
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| 3. |
- Augulis, Ramunas, et al.
(författare)
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Detector and dispersive delay calibration issues in broadband 2D electronic spectroscopy
- 2013
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Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 30:6, s. 1770-1774
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Tidskriftsartikel (refereegranskat)abstract
- Precision of two-dimensional (2D) electronic spectroscopy can be affected by imprecise calibration of the optical spectrometer and coherence time delay line. This would result in 2D spectral line shapes with twisted phase, where absorptive and dispersive parts of the signal are mixed and unrecoverable. We demonstrate two efficient and easily implementable techniques for precise spectrometer and wedge-based delay line calibration that assure acquisition of correct spectral phase in 2D spectroscopy measurements. (C) 2013 Optical Society of America
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| 4. |
- Augulis, Ramunas, et al.
(författare)
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Two-dimensional electronic spectroscopy with double modulation lock-in detection: enhancement of sensitivity and noise resistance
- 2011
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Ingår i: Optics Express. - 1094-4087. ; 19:14, s. 13126-13133
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Tidskriftsartikel (refereegranskat)abstract
- In many potential applications of two-dimensional (2D) electronic spectroscopy the excitation energies per pulse are strictly limited, while the samples are strongly scattering. We demonstrate a technique, based on double-modulation of incident laser beams with mechanical choppers, which can be implemented in almost any non-collinear four wave mixing scheme including 2D spectroscopy setup. The technique virtually eliminates artifacts or "ghost" signals in 2D spectra, which arise due to scattering and accumulation of long-lived species. To illustrate the advantages of the technique, we show a comparison of porphyrin J-aggregate 2D spectra obtained with different methods following by discussion. (C) 2011 Optical Society of America
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| 5. |
- Bakulin, Artem A, et al.
(författare)
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Real-time observation of multiexcitonic states in ultrafast singlet fission using coherent 2D electronic spectroscopy.
- 2016
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Ingår i: Nature Chemistry. - : Springer Science and Business Media LLC. - 1755-4330 .- 1755-4349. ; 8:1, s. 16-23
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Tidskriftsartikel (refereegranskat)abstract
- Singlet fission is the spin-allowed conversion of a spin-singlet exciton into a pair of spin-triplet excitons residing on neighbouring molecules. To rationalize this phenomenon, a multiexcitonic spin-zero triplet-pair state has been hypothesized as an intermediate in singlet fission. However, the nature of the intermediate states and the underlying mechanism of ultrafast fission have not been elucidated experimentally. Here, we study a series of pentacene derivatives using ultrafast two-dimensional electronic spectroscopy and unravel the origin of the states involved in fission. Our data reveal the crucial role of vibrational degrees of freedom coupled to electronic excitations that facilitate the mixing of multiexcitonic states with singlet excitons. The resulting manifold of vibronic states drives sub-100 fs fission with unity efficiency. Our results provide a framework for understanding singlet fission and show how the formation of vibronic manifolds with a high density of states facilitates fast and efficient electronic processes in molecular systems.
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| 6. |
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| 7. |
- Billsten, Helena, et al.
(författare)
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Dynamics of vibrational relaxation in the S-1 state of carotenoids having 11 conjugated C=C bonds
- 2002
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Ingår i: Chemical Physics Letters. - 0009-2614. ; 355:5-6, s. 465-470
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Tidskriftsartikel (refereegranskat)abstract
- Transient absorption spectra and kinetics in the 470-650 nm region were recorded for lycopene, P-carotene and zeaxanthin, all carotenoids with 11 conjugated double bonds, in two solvents with different polarity. Analysis of the red wing of the carotenoid SI-S, transition revealed presence of a pronounced shoulder at early delay times. The kinetics recorded at this low-energy shoulder of the SI-S, transition yields an additional decay component of 500-800 fs in addition to the main S, decay. This dynamics is ascribed to a vibrational relaxation in the S, state of the carotenoids. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 8. |
- Bruder, Lukas, et al.
(författare)
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Generation and compression of 10-fs deep ultraviolet pulses at high repetition rate using standard optics
- 2021
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Ingår i: Optics Express. - 1094-4087. ; 29:16, s. 25593-25604
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Tidskriftsartikel (refereegranskat)abstract
- The generation and characterization of ultrashort laser pulses in the deep ultraviolet spectral region is challenging, especially at high pulse repetition rates and low pulse energies. Here, we combine achromatic second harmonic generation and adaptive pulse compression for the efficient generation of sub-10 fs deep ultraviolet laser pulses at a laser repetition rate of 200 kHz. Furthermore, we simplify the pulse compression scheme and reach pulse durations of ≈10 fs without the use of adaptive optics. We demonstrate straight-forward tuning from 250 to 320 nm, broad pulse spectra of up to 63 nm width, excellent stability and a high robustness against misalignment. These features make the approach appealing for numerous spectroscopy and imaging applications.
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| 9. |
- Bukartė, Eglė, et al.
(författare)
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Dynamic band-shift signal in two-dimensional electronic spectroscopy: A case of bacterial reaction center
- 2021
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 154:11
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Tidskriftsartikel (refereegranskat)abstract
- Optical nonlinear spectroscopies carry a high amount of information about the systems under investigation; however, as they report polarization signals, the resulting spectra are often congested and difficult to interpret. To recover the landscape of energy states and physical processes such as energy and electron transfer, a clear interpretation of the nonlinear signals is prerequisite. Here, we focus on the interpretation of the electrochromic band-shift signal, which is generated when an internal electric field is established in the system following optical excitation. Whereas the derivative shape of the band-shift signal is well understood in transient absorption spectroscopy, its emergence in two-dimensional electronic spectroscopy (2DES) has not been discussed. In this work, we employed 2DES to follow the dynamic band-shift signal in reaction centers of purple bacteria Rhodobacter sphaeroides at 77 K. The prominent two-dimensional derivative-shape signal appears with the characteristic formation time of the charge separated state. To explain and characterize the band-shift signal, we use expanded double-sided Feynman diagram formalism. We propose to distinguish two types of Feynman diagrams that lead to signals with negative amplitude: excited state absorption and re-excitation. The presented signal decomposition and modeling analysis allows us to recover precise electrochromic shifts of accessory bacteriochlorophylls, identify additional signals in the B band range, and gain a further insight into the electron transfer mechanism. In a broader perspective, expanded Feynman diagram formalism will allow for interpretation of all 2D signals in a clearer and more intuitive way and therefore facilitate studying the underlying photophysics.
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| 10. |
- Bukartė, Eglė, et al.
(författare)
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Revealing vibronic coupling in chlorophyll c1 by polarization-controlled 2D electronic spectroscopy
- 2020
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Ingår i: Chemical Physics. - : Elsevier BV. - 0301-0104. ; 530
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Tidskriftsartikel (refereegranskat)abstract
- Vibronic coupling between molecules has been recently discussed to play an important role in photosynthetic functions. Furthermore, this type of coupling between electronic states has been suggested to define photophysical properties of chlorophylls, a family of photosynthetic molecules. However, experimental investigation of vibronic coupling presents a major challenge. One subtle way to study vibronic coupling is by excitation and observation of superpositions of vibrational states via transitions to vibronically mixed states. Such superpositions, called coherences, are then observed as quantum beats in non-linear spectroscopy experiments. Here we present polarization-controlled two-dimensional electronic spectroscopy study of the chlorophyll c1 molecule at cryogenic (77 K) temperature. By applying complex analysis to the oscillatory signals we are able to unravel vibronic coupling in this molecule. The vibronic mixing picture that we see is much more complex than was thought before.
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