| 1. |
- Biegert, Jens, et al.
(författare)
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Control of the frequency chirp rate of high harmonic pulses
- 2004
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Ingår i: Springer Series in Chemical Physics. - 0172-6218. ; 79, s. 204-206
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Tidskriftsartikel (refereegranskat)abstract
- We measured the frequency chirp rate of harmonics 13 to 23 in argon by cross-correlation with a short femtosecond probe pulse. We directly measured the negative chirp due to the atomic dipole phase and demonstrated that an additional chirp on the pump pulse was transferred to the qth harmonic as q times the fundamental chirp.
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| 2. |
- Brüggemann, Ben, et al.
(författare)
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Ultrafast exciton dynamics in molecular systems
- 2007
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Ingår i: Quantum Dynamics of Complex Molecular Systems. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0172-6218. - 9783540344605 ; , s. 31-55
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Konferensbidrag (refereegranskat)abstract
- The theory of subpicosecond Frenkel exciton dynamics in molecular systems is reviewed with emphasis on a stepwise imp loved description of the coupling to intra- and intermolecular vibrations. After introducing the concept of multiexciton states the motion of electronic Frenkel excitons as they appear in light harvesting antennae of photosynthetic organisms is discussed. The description is based on a multiexciton density matrix theory which accounts for the exciton-vibrational coupling in a perturbative manner. Some improvements of this density matrix theory as suggested in literature are shortly mentioned. Afterwards, vibrational Frenkel excitons as found in polypeptides are considered. By utilizing the multiconfiguration time-dependent Hartree method an exact description of the coupling to longitudinal vibrations of the peptide chain becomes possible. The discussion of the computed transient infrared absorption spectra is supported by the introduction of adiabatic single- and two-exciton states.
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| 3. |
- Charalambidis, Dimitris, et al.
(författare)
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The extreme light infrastructure—attosecond light pulse source (ELI-ALPS) project
- 2017. - 9783319648392
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Ingår i: Springer Series in Chemical Physics. - Cham : Springer International Publishing. - 0172-6218. ; :9783319648392, s. 181-218
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Bokkapitel (refereegranskat)abstract
- Globally, large international research infrastructures have over many decades promoted excellence in science and technology. Aligned with the international practice, the Europe Strategy Forum for Research Infrastructures (ESFRI) has developed and keeps updating a roadmap for research infrastructures. The Extreme Light Infrastructure (ELI) is one of the two large scale Laser Research Infrastructures (RI) proposed in the ESFRI Roadmap published in 2006. ELI aims to provide access to some of the most intense world-wide lasers for the international scientific user community, as well as secondary radiation and particle sources driven by them, offering to the users new interdisciplinary research opportunities. ELI is currently implemented as a distributed infrastructure in three pillars: ELI-Beamlines (ELI-BL) in Dolní Břežany, Czech Republic, ELI-Attosecond Light Pulse Source (ELI-ALPS) in Szeged, Hungary and ELI-Nuclear Physics (ELI-NP) in Magurele, Romania. This chapter is devoted to introduce the Hungarian pillar, ELI-ALPS, which will be operational in Szeged in 2018, with the primary mission to provide to the users the highest laboratory spatiotemporal resolution and a secondary mission to contribute to the technological development towards 200 petawatt (PW) lasers for high-field science, which is the ultimate goal of the ELI project. The chapter includes descriptions of the primary and secondary sources, while emphasis is given to selected examples of the scientific case of ELI-ALPS, presenting unique access offered by the technologies to be hosted in the infrastructure.
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| 4. |
- Christensson, Niklas, et al.
(författare)
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Determining Vibrational Huang-Rhys Factors by Photon Echo Spectroscopy
- 2009
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Ingår i: Ultrafast Phenomena XVI. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0172-6218. ; 92, s. 334-336
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Konferensbidrag (refereegranskat)abstract
- Electronic and vibrational dephasing dynamics of Rhodamine 800 has been studied with 3PEPS. With careful analysis, the S-factors of the vibrational modes can be accurately determined. The vibrational dephasing rate displays abnormal frequency dependence.
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| 5. |
- Jesorka, Aldo, 1967, et al.
(författare)
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Controlling Chemistry in Dynamic Nanoscale Systems
- 2010
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Ingår i: Springer Series in Chemical Physics. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0172-6218. - 9783642025969 ; 96, s. 449-468
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The biological cell, the fundamental building block of the living world, is a complex maze of compartmentalized biochemical reactors that embed tens of thousands of chemical reactions running in parallel. Several, if not all, reactors are systematically interconnected by a web of nanofluidic transporters, such as nanotubes, vesicles, and membrane pores with ever-changing shapes and structures [1]. To initiate, terminate, or control chemical reactions, small-scale poly-/pleiomorphic systems undergo rapid and violent shape changes with energy barriers close to kBT , where, due to the small dimensions, diffusional mixing of reactants is rapid. The geometry, i.e. volume, and shape changes can be utilized to control both kinetic and thermodynamic properties of the system. This is in sharp contrast to the man-made macroscopic bioreactors, in which mixing of reactants is aided by mechanical means, such as stirring or sonication, under the assumption that reactions take place in volumes that do not change over time. Such reaction volumes are compact, like a sphere, a cube, or a cylinder, and do not provide for variation of shape. Ordinarily, reaction rates, mechanisms, and thermodynamic properties of chemical reactions in condensed media are based on these assumptions. A number of important questions and challenges arise from these facts. For example, how will we achieve fundamental understanding of how reactor shape affects chemistry on the nanoscale, how do we develop appropriate and powerful experimental model systems, and last but not least what impact will this knowledge have on the design and function of nanotechnological devices with new operation modes derived from natural principles.
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| 6. |
- Rouzée, Arnaud, et al.
(författare)
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Molecular Movies from Molecular Frame Photoelectron Angular Distribution (MF-PAD) Measurements
- 2014
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Ingår i: Ultrafast Phenomena in Molecular Sciences : Femtosecond Physics and Chemistry - Femtosecond Physics and Chemistry. - Cham : Springer International Publishing. - 0172-6218. - 9783319020501 ; 107, s. 1-24
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Bokkapitel (refereegranskat)abstract
- We discuss recent and on-going experiments, where molecular frame photoelectron angular distributions (MFPADs) of high kinetic energy photoelectrons are measured in order to determine the time evolution of molecular structures in the course of a photochemical event. These experiments include, on the one hand, measurements where single XUV/X-ray photons, obtained from a free electron laser (FEL) or by means of high-harmonic generation (HHG), are used to eject a high energy photoelectron, and, on the other hand, measurements where a large number of mid-infrared photons are absorbed in the course of strong-field ionization. In the former case, first results indicate a manifestation of the both the electronic orbital and the molecular structure in the angle-resolved photoelectron distributions, while in the latter case novel holographic structures are measured that suggest that both the molecular structure and ultrafast electronic rearrangement processes can be studied with a time-resolution that reaches down into the attosecond and few-femtosecond domain.
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| 7. |
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| 8. |
- Stierle, Andreas, et al.
(författare)
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Surface-sensitive X-ray diffraction across the pressure gap
- 2017
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Ingår i: Springer Series in Chemical Physics. - Cham : Springer International Publishing. - 0172-6218. ; 114, s. 59-87
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Bokkapitel (refereegranskat)abstract
- In this chapter surface-sensitive X-ray diffraction is introduced as an important crystallographic tool for the investigation of surfaces and nanostructures under high pressure reaction conditions and elevated temperatures which are relevant for industrial catalysis. After the introduction surface-sensitive X-ray diffraction methods are briefly explained and specialized instrumentation developed for the in situ investigation of surfaces and nanostructures across the pressure gap is presented combined with simultaneous measurement of the concentrations of reactants and products. In the following an overview of the experimental results is given: First the (near)-ambient pressure oxidation of 3d, 4d, and 5d transition metals is discussed which are relevant for oxidation catalysis. Afterwards catalytic reaction experiments in batch mode are reported, followed by an overview of current research using a flow reactor for surface-sensitive X-ray diffraction. Finally a perspective is given for future research directions.
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| 9. |
- Zetterberg, Johan, et al.
(författare)
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Planar laser induced fluorescence applied to catalysis
- 2017
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Ingår i: Springer Series in Chemical Physics. - Cham : Springer International Publishing. - 0172-6218. ; 114, s. 131-149
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Bokkapitel (refereegranskat)abstract
- In this chapter we describe Planar Laser Induced Fluorescence (PLIF) to investigate the reactants or products in the vicinity of a catalyst at semi-realistic conditions. PLIF provides a 2D view of the gas-phase distribution of a pre-chosen gas. Here we present PLIF results from CO2 and CO from the oxidation of CO into CO2 by Pd single crystals and by various powder catalysts as well as from NH3 from the oxidation of NH3 above a Ag/Al2O3 powder catalyst.We describe our experimental set-up in detail, and the laser instrumentation needed to enable detectable gas fluorescence from CO2, CO, and NH3, respectively. Further, intensity corrections of the PLIF signal due to scattering and temperature effects are described. In the case of the CO oxidation, the results directly show the creation of a CO2 boundary layer and thus a drastic change of the gas-phase composition close to the catalyst surface, illustrating the effect of gas diffusion and reaction speed, which in turn should affect the surface structure of the active catalyst. The 2D character of the PLIF images is used to investigate differences in catalyst activity by studying adjacent catalysts in the reaction cell during the reaction, and a solution to avoid spill-over effects between catalysts in the same reactor is presented. The results from PLIF images of CO of the same reaction show the corresponding depletion of the PLIF intensity above the catalyst, in accordance with observations from other techniques confirming the drastic difference between the gas composition close to the catalyst and at the inlet or outlet of the reactor. Finally we present NH3 PLIF results from above a Ag/Al2O3 powder catalyst while the NH3 is being oxidized in an oxidizing environment with the assistance of H2.
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