| 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. |
- 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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| 3. |
- 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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| 4. |
- Butkus, Vytautas, et al.
(författare)
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Distinctive character of electronic and vibrational coherences in disordered molecular aggregates
- 2013
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 587, s. 93-98
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Tidskriftsartikel (refereegranskat)abstract
- Coherent dynamics of coupled molecules are effectively characterized by the two-dimensional electronic spectroscopy. Depending on the coupling between electronic and vibrational states, oscillating signals of purely electronic, purely vibrational or mixed character are observed with the help of oscillation maps, constructed from time-resolved spectra. Amplitude of beatings caused by electronic coherences is heavily affected by energetic disorder and consequently electronic coherences are quickly dephased. Beatings with vibrational character weakly depend on the disorder, ensuring their long-time survival. We show that detailed modeling of two-dimensional spectroscopy signals of molecular aggregates provides direct information on the origin of the coherent beatings. (C) 2013 Elsevier B. V. All rights reserved.
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| 5. |
- Butkus, Vytautas, et al.
(författare)
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Phase relationships of spectral oscillations in 2D molecular spectroscopy
- 2013
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Ingår i: 18th International Conference on Ultrafast Phenomena, UP 2012. - : EDP Sciences. - 9782759809561 ; 41
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Konferensbidrag (refereegranskat)abstract
- Spectral oscillations in 2D molecular spectroscopy of the displaced oscillator system and their phase relationships are analyzed. The phase maps of the dispersive and absolute-valued signals give hints for experimental probing of peak oscillations.
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| 6. |
- Butkus, Vytautas, et al.
(författare)
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Vibrational vs. electronic coherences in 2D spectrum of molecular systems
- 2012
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 545, s. 40-43
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional spectroscopy has recently revealed the oscillatory behavior of the excitation dynamics of molecular systems. However, in the majority of cases there is considerable debate over what is actually being observed: excitonic or vibrational wavepacket motion or evidence of quantum transport. In this letter we present a method for distinguishing between vibrational and excitonic wavepacket motion, based on the phase and amplitude relationships of oscillations of distinct peaks as revealed through a fundamental analysis of the two-dimensional spectra of two representative systems. (C) 2012 Elsevier B.V. All rights reserved.
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| 7. |
- Christensson, Niklas, et al.
(författare)
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Origin of the Bathochromic Shift of Astaxanthin in Lobster Protein: 2D Electronic Spectroscopy Investigation of beta-Crustacyanin
- 2013
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Ingår i: The Journal of Physical Chemistry Part B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 117:38, s. 11209-11219
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Tidskriftsartikel (refereegranskat)abstract
- We report on ultrafast spectroscopy study of beta-crustacyanin, the carotenoprotein responsible for the coloration of the lobster shell. beta-Crustacyanin is formed by two closely positioned astaxanthin molecules encapsulated in protein. The 2D electronic spectroscopy together with two-color pump-probe was applied to investigate the electronic structure, the excited-state dynamics, and the influence of the excitonic interaction between the two carotenoids in beta-crustacyanin. By using the similar to 20 Is laser pulses tuned to absorption bands of the S-0-S-2 and S-1-S-n transitions of carotenoids, we were able to trace full excitation relaxation dynamics, starting with S-2-S-1 relaxation on the similar to 30 fs time scale and finishing with the ground-state recovery of 3.2 ps. Superimposed on the relaxation dynamics in the 2D spectra, we observed long-lived beating signals at the characteristic frequencies of astaxanthin vibrational modes. We assign these oscillations to the ground-state vibrational wavepacket dynamics. All major features of the 2ll spectra, including amplitude and phase maps of the long-lived oscillations, were reproduced by employing the exciton-vibronic model. Consistent modeling of all optical properties of beta-crustacyanin (including absorption and circular dichroism spectra) points to the relatively weak coupling between the two astaxanthin molecules (similar to 250 cm(-1)). This implies that the excitonic coupling provides insignificant contribution to the bathochromic shift in beta-crustacyanin. We discuss the origin of the shift and propose that it is caused by two major effects: conformational changes of astaxanthin molecules (increase in effective conjugation length) together with increased charge-transfer character of the S-2 state. We put the bathochromic shift in the broad perspective of other "blue" carotenoids properties.
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| 8. |
- Dostal, Jakub, et al.
(författare)
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2D Electronic Spectroscopy Reveals Excitonic Structure in the Baseplate of a Chlorosome
- 2014
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Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 5:10, s. 1743-1747
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Tidskriftsartikel (refereegranskat)abstract
- In green photosynthetic bacteria, the chlorosome baseplate mediates excitation energy transfer from the interior of the light-harvesting chlorosome toward the reaction centers. However, the electronic states of the baseplate remain unexplored, hindering the mechanistic understanding of the baseplate as an excitation energy collector and mediator. Here we use two-dimensional spectroscopy to study the excited state structure and internal energy relaxation in the baseplate of green sulfur bacterium Chlorobaculum tepidum. We resolved an exciton system with four energy states, indicating that the organization of the pigments in the baseplate is more complex than was thought before and constitutes at least four bacteriochlorophyll molecules in a close contact. Based on the finding that the energy of the baseplate states is in the same range as in the adjacent Fenna-Matthews-Olson complex, we propose a "lateral" energy transfer pathway, where excitation energy can flow through the photosynthetic unit via all the states of individual complexes.
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| 9. |
- Dostal, Jakub, et al.
(författare)
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Fast Exciton Dynamics and Coherent Oscillations Revealed by Coherent 2D Spectroscopy in Chlorosomes
- 2013
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Ingår i: XVIIITH International Conference on Ultrafast Phenomena. - : EDP Sciences. - 2100-014X .- 2101-6275. ; 41
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Konferensbidrag (refereegranskat)abstract
- In this study ultrafast energy transfer dynamics in chlorosomes from sulphur bacterium Chlorobaculum tepidum were explored by means of coherent electronic two-dimensional spectroscopy. Observed sub-100 fs dynamics were attributed to incoherent downhill excitation diffusion between disordered domains within chlorosomes. At the same time vibrational coherent oscillations were investigated on the longer timescales.
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| 10. |
- Dostal, Jakub, et al.
(författare)
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Two-Dimensional Electronic Spectroscopy Reveals Ultrafast Energy Diffusion in Chlorosomes.
- 2012
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 134:28, s. 11611-11617
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Tidskriftsartikel (refereegranskat)abstract
- Chlorosomes are light-harvesting antennae that enable exceptionally efficient light energy capture and excitation transfer. They are found in certain photosynthetic bacteria, some of which live in extremely low-light environments. In this work, chlorosomes from the green sulfur bacterium Chlorobaculum tepidum were studied by coherent electronic two-dimensional (2D) spectroscopy. Previously uncharacterized ultrafast energy transfer dynamics were followed, appearing as evolution of the 2D spectral line-shape during the first 200 fs after excitation. Observed initial energy flow through the chlorosome is well explained by effective exciton diffusion on a sub-100 fs time scale, which assures efficiency and robustness of the process. The ultrafast incoherent diffusion-like behavior of the excitons points to a disordered energy landscape in the chlorosome, which leads to a rapid loss of excitonic coherences between its structural subunits. This disorder prevents observation of excitonic coherences in the experimental data and implies that the chlorosome as a whole does not function as a coherent light-harvester.
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