| 1. |
- Bergues, B., et al.
(författare)
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Nonlinear interaction of 100-eV attosecond XUV-pulses with core electrons in Xenon
- 2018
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Ingår i: Optics InfoBase Conference Papers. - : Optica Publishing Group. - 9781557528209
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Konferensbidrag (refereegranskat)abstract
- We demonstrate multiphoton ionization of inner-shell electrons in Xenon with 100-eV attosecond pulses. This was achieved with a novel XUV source based on high-harmonic generation in the gas phase driven with multi-TW few-cycle laser pulses.
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| 2. |
- Bergues, B., et al.
(författare)
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Tabletop nonlinear optics in the 100-eV spectral region
- 2018
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Ingår i: Optica. - : Optical Society of America. - 2334-2536. ; 5:3, s. 237-242
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Tidskriftsartikel (refereegranskat)abstract
- Nonlinear light-matter interactions in the extreme ultraviolet (XUV) are a prerequisite to perform XUV-pump/XUV-probe spectroscopy of core electrons. Such interactions are now routinely investigated at free-electron laser (FEL) facilities. Yet, electron dynamics are often too fast to be captured with the femtosecond resolution of state-of-the-art FELs. Attosecond pulses from laser-driven XUV-sources offer the necessary temporal resolution. However, intense attosecond pulses supporting nonlinear processes have only been available for photon energy below 50 eV, precluding XUV-pump/XUV-probe investigation of typical inner-shell processes. Here, we surpass this limitation by demonstrating two-photon absorption from inner electronic shells of xenon at photon energies around 93 eV and 115 eV. This advance opens the door for attosecond real-time observation of nonlinear electron dynamics deep inside atoms.
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| 3. |
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| 4. |
- Buck, A., et al.
(författare)
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Shock-Front Injector for High-Quality Laser-Plasma Acceleration
- 2013
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 110:18
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Tidskriftsartikel (refereegranskat)abstract
- We report the generation of stable and tunable electron bunches with very low absolute energy spread (ΔE≈5 MeV) accelerated in laser wakefields via injection and trapping at a sharp downward density jump produced by a shock front in a supersonic gas flow. The peak of the highly stable and reproducible electron energy spectrum was tuned over more than 1 order of magnitude, containing a charge of 1–100 pC and a charge per energy interval of more than 10 pC/MeV. Laser-plasma electron acceleration with Ti:sapphire lasers using this novel injection mechanism provides high-quality electron bunches tailored for applications.
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| 5. |
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| 6. |
- Haasen, C., et al.
(författare)
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Cocaine use in Europe - a multi-centre study : Methodology and prevalence estimates
- 2004
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Ingår i: European Addiction Research. - 1022-6877 .- 1421-9891. ; 10:4, s. 139-146
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Tidskriftsartikel (refereegranskat)abstract
- An increase in the use of cocaine and crack in several parts of Europe has raised the question whether this trend is similar to that of the USA in the 1980s. However, research in the field of cocaine use in Europe has been only sporadic. Therefore, a European multi-centre and multi-modal project was designed to study specific aspects of cocaine and crack use in Europe, in order to develop guidelines for public health strategies. Data on prevalence rates were analysed for the general population and for specific subgroups. Despite large differences between countries in the prevalence of cocaine use in the general population, most countries show an increase in the last few years. The highest rate with a lifetime prevalence of 5.2% was found for the United Kingdom, although with a plateau effect around the year 2000. With regard to specific subgroups, three groups seem to show a higher prevalence than the general population: (1) youth, especially in the party scene; (2) socially marginalized groups, such as homeless and prostitutes or those found in open drug scenes; (3) opiate-dependent patients in maintenance treatment who additionally use cocaine. Specific strategies need to be developed to address problematic cocaine use in these subgroups.
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| 7. |
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| 8. |
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| 9. |
- Major, B., et al.
(författare)
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Investigation of high harmonic generation using a high-power, 5-fs laser in a loose-focusing geometry
- 2017
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Ingår i: 2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC). - : IEEE. - 9781509067367
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Konferensbidrag (refereegranskat)abstract
- Summary form only given. Since its first observation almost three decades ago high-order harmonic generation (HHG) in gases became a reliable source of extreme ultraviolet (XUV) pulses, which gave the possibility to study electronic processes on their natural timescale [1, 2]. While the main building blocks of the experimental setups for gas HHG are the same in almost all cases, the focusing or medium geometry varies from realization to realization based on, for example, the available laser power [3, 4].In this work we study HHG in a loose focusing geometry by focusing a ~50-mm diameter (FWHM) beam with a mirror of 16-m focal length (f-number ~320). The main subject of this analysis is to compare low pressure - long interaction length (few millibars and tens of centimeters) with high pressure - short medium (hundreds of millibars and a few millimeters) scenarios and understand the underlying reasons for the observed XUV radiation parameters. The experiments are carried out with on target 35 mJ, sub-5 fs, 740 nm central wavelength pulses provided by an optical parametric synthesizer [5], producing high-energy pulses at the 100 eV spectral region [6]. The theoretical analysis is performed by simulation code based on a three-dimensional nonadiabatic model [7,8]. The good agreement between the experimental and simulation data (see Fig. 1) allows us to use the theoretical findings to gain better insight on the exact phase-matching processes providing the observed features. This detailed description is used to draw general conclusions of the high-harmonic generation process.
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| 10. |
- Prinzleve, M., et al.
(författare)
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Cocaine use in Europe - a multi-centre study : Patterns of use in different groups
- 2004
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Ingår i: European Addiction Research. - 1022-6877 .- 1421-9891. ; 10:4, s. 147-155
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Tidskriftsartikel (refereegranskat)abstract
- AIM: The study investigates patterns of cocaine powder and crack cocaine use of different groups in nine European cities. DESIGN, SETTING, PARTICIPANTS: Multi-centre cross-sectional study conducted in Barcelona, Budapest, Dublin, Hamburg, London, Paris, Rome, Vienna, and Zurich. Data were collected by structured face-to-face interviews. The sample comprises 1,855 cocaine users out of three subgroups: 632 cocaine users in addiction treatment, mainly maintenance treatment; 615 socially marginalized cocaine users not in treatment, and 608 socially integrated cocaine users not in treatment. MEASUREMENTS: Use of cocaine powder, crack cocaine and other substances in the last 30 days, routes of administration, and lifetime use of cocaine powder and crack cocaine. Findings: The marginalized group showed the highest intensity of cocaine use, the highest intensity of heroin use and of multiple substance use. 95% of the integrated group snorted cocaine powder, while in the two other groups, injecting was quite prevalent, but with huge differences between the cities. 96% of all participants had used at least one other substance in addition to cocaine in the last 30 days. CONCLUSIONS: The use of cocaine powder and crack cocaine varies widely between different groups and between cities. Nonetheless, multiple substance use is the predominating pattern of cocaine use, and the different routes of administration have to be taken into account.
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| 11. |
- Reimers, Jeffrey R., et al.
(författare)
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Challenges facing an understanding of the nature of low-energy excited states in photosynthesis
- 2016
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Ingår i: Biochimica et Biophysica Acta - Bioenergetics. - : Elsevier BV. - 0005-2728 .- 1879-2650. ; 1857:9, s. 1627-1640
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Forskningsöversikt (refereegranskat)abstract
- While the majority of the photochemical states and pathways related to the biological capture of solar energy are now well understood and provide paradigms for artificial device design, additional low-energy states have been discovered in many systems with obscure origins and significance. However, as low-energy states are naively expected to be critical to function, these observations pose important challenges. A review of known properties of low energy states covering eight photochemical systems, and options for their interpretation, are presented. A concerted experimental and theoretical research strategy is suggested and outlined, this being aimed at providing a fully comprehensive understanding.
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| 12. |
- Rivas, D. E., et al.
(författare)
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Next Generation Driver for Attosecond and Laser-plasma Physics
- 2017
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- The observation and manipulation of electron dynamics in matter call for attosecond light pulses, routinely available from high-order harmonic generation driven by few-femtosecond lasers. However, the energy limitation of these lasers supports only weak sources and correspondingly linear attosecond studies. Here we report on an optical parametric synthesizer designed for nonlinear attosecond optics and relativistic laser-plasma physics. This synthesizer uniquely combines ultra-relativistic focused intensities of about 10(20)W/cm(2) with a pulse duration of sub-two carrier-wave cycles. The coherent combination of two sequentially amplified and complementary spectral ranges yields sub-5-fs pulses with multi-TW peak power. The application of this source allows the generation of a broad spectral continuum at 100-eV photon energy in gases as well as high-order harmonics in relativistic plasmas. Unprecedented spatio-temporal confinement of light now permits the investigation of electric-field-driven electron phenomena in the relativistic regime and ultimately the rise of next-generation intense isolated attosecond sources.
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| 13. |
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