The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Andreas Tünnermann - One of the best experts on this subject based on the ideXlab platform.
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Exploring new avenues in high repetition rate table-top coherent extreme Ultraviolet Sources
Light: Science & Applications, 2015Co-Authors: Steffen Hädrich, Manuel Krebs, Armin Hoffmann, Arno Klenke, Jan Rothhardt, Jens Limpert, Andreas TünnermannAbstract:A photonic-crystal fibre filled with krypton gas has been used to realize an extreme-Ultraviolet source with a megahertz repetition rate. Applications such as photoelectron spectroscopy and coherent diffractive imaging ideally require extreme-Ultraviolet Sources with a high photon flux and a high repetition rate, but achieving both properties simultaneously is challenging. Now, scientists in Jena, Germany, have solved this problem by using a krypton-filled kagome fibre to nonlinearly compress laser pulses at a rate of 10.7 megahertz. They then used the rapid stream of compressed pulses to drive high-harmonic generation in a gas jet. This resulted in the generation of over 50 microwatts at a photon energy of 27.7 electron volts. The approach could lead to a new breed of more compact and efficient high-harmonic-generation Sources.
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Exploring new avenues in high repetition rate table-top coherent extreme Ultraviolet Sources
Light: Science & Applications, 2015Co-Authors: Steffen Hädrich, Manuel Krebs, Armin Hoffmann, Arno Klenke, Jan Rothhardt, Jens Limpert, Andreas TünnermannAbstract:The process of high harmonic generation (HHG) enables the development of table-top Sources of coherent extreme Ultraviolet (XUV) light. Although these are now matured Sources, they still mostly rely on bulk laser technology that limits the attainable repetition rate to the low kilohertz regime. Moreover, many of the emerging applications of such light Sources (e.g., photoelectron spectroscopy and microscopy, coherent diffractive imaging, or frequency metrology in the XUV spectral region) require an increase in the repetition rate. Ideally, these Sources are operated with a multi-MHz repetition rate and deliver a high photon flux simultaneously. So far, this regime has been solely addressed using passive enhancement cavities together with low energy and high repetition rate lasers. Here, a novel route with significantly reduced complexity (omitting the requirement of an external actively stabilized resonator) is demonstrated that achieves the previously mentioned demanding parameters. A krypton-filled Kagome photonic crystal fiber is used for efficient nonlinear compression of 9 µJ, 250 fs pulses leading to ∼7 µJ, 31 fs pulses at 10.7 MHz repetition rate. The compressed pulses are used for HHG in a gas jet. Particular attention is devoted to achieving phase-matched (transiently) generation yielding >10^13 photons s^−1 (>50 µW) at 27.7 eV. This new spatially coherent XUV source improved the photon flux by four orders of magnitude for direct multi-MHZ experiments, thus demonstrating the considerable potential of this source. A photonic-crystal fibre filled with krypton gas has been used to realize an extreme-Ultraviolet source with a megahertz repetition rate. Applications such as photoelectron spectroscopy and coherent diffractive imaging ideally require extreme-Ultraviolet Sources with a high photon flux and a high repetition rate, but achieving both properties simultaneously is challenging. Now, scientists in Jena, Germany, have solved this problem by using a krypton-filled kagome fibre to nonlinearly compress laser pulses at a rate of 10.7 megahertz. They then used the rapid stream of compressed pulses to drive high-harmonic generation in a gas jet. This resulted in the generation of over 50 microwatts at a photon energy of 27.7 electron volts. The approach could lead to a new breed of more compact and efficient high-harmonic-generation Sources.
Steffen Hädrich - One of the best experts on this subject based on the ideXlab platform.
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Exploring new avenues in high repetition rate table-top coherent extreme Ultraviolet Sources
Light: Science & Applications, 2015Co-Authors: Steffen Hädrich, Manuel Krebs, Armin Hoffmann, Arno Klenke, Jan Rothhardt, Jens Limpert, Andreas TünnermannAbstract:A photonic-crystal fibre filled with krypton gas has been used to realize an extreme-Ultraviolet source with a megahertz repetition rate. Applications such as photoelectron spectroscopy and coherent diffractive imaging ideally require extreme-Ultraviolet Sources with a high photon flux and a high repetition rate, but achieving both properties simultaneously is challenging. Now, scientists in Jena, Germany, have solved this problem by using a krypton-filled kagome fibre to nonlinearly compress laser pulses at a rate of 10.7 megahertz. They then used the rapid stream of compressed pulses to drive high-harmonic generation in a gas jet. This resulted in the generation of over 50 microwatts at a photon energy of 27.7 electron volts. The approach could lead to a new breed of more compact and efficient high-harmonic-generation Sources.
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Exploring new avenues in high repetition rate table-top coherent extreme Ultraviolet Sources
Light: Science & Applications, 2015Co-Authors: Steffen Hädrich, Manuel Krebs, Armin Hoffmann, Arno Klenke, Jan Rothhardt, Jens Limpert, Andreas TünnermannAbstract:The process of high harmonic generation (HHG) enables the development of table-top Sources of coherent extreme Ultraviolet (XUV) light. Although these are now matured Sources, they still mostly rely on bulk laser technology that limits the attainable repetition rate to the low kilohertz regime. Moreover, many of the emerging applications of such light Sources (e.g., photoelectron spectroscopy and microscopy, coherent diffractive imaging, or frequency metrology in the XUV spectral region) require an increase in the repetition rate. Ideally, these Sources are operated with a multi-MHz repetition rate and deliver a high photon flux simultaneously. So far, this regime has been solely addressed using passive enhancement cavities together with low energy and high repetition rate lasers. Here, a novel route with significantly reduced complexity (omitting the requirement of an external actively stabilized resonator) is demonstrated that achieves the previously mentioned demanding parameters. A krypton-filled Kagome photonic crystal fiber is used for efficient nonlinear compression of 9 µJ, 250 fs pulses leading to ∼7 µJ, 31 fs pulses at 10.7 MHz repetition rate. The compressed pulses are used for HHG in a gas jet. Particular attention is devoted to achieving phase-matched (transiently) generation yielding >10^13 photons s^−1 (>50 µW) at 27.7 eV. This new spatially coherent XUV source improved the photon flux by four orders of magnitude for direct multi-MHZ experiments, thus demonstrating the considerable potential of this source. A photonic-crystal fibre filled with krypton gas has been used to realize an extreme-Ultraviolet source with a megahertz repetition rate. Applications such as photoelectron spectroscopy and coherent diffractive imaging ideally require extreme-Ultraviolet Sources with a high photon flux and a high repetition rate, but achieving both properties simultaneously is challenging. Now, scientists in Jena, Germany, have solved this problem by using a krypton-filled kagome fibre to nonlinearly compress laser pulses at a rate of 10.7 megahertz. They then used the rapid stream of compressed pulses to drive high-harmonic generation in a gas jet. This resulted in the generation of over 50 microwatts at a photon energy of 27.7 electron volts. The approach could lead to a new breed of more compact and efficient high-harmonic-generation Sources.
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sensitivity calibration of an imaging extreme Ultraviolet spectrometer detector system for determining the efficiency of broadband extreme Ultraviolet Sources
Review of Scientific Instruments, 2013Co-Authors: Silvio Fuchs, Steffen Hädrich, Manuel Krebs, Christian Rodel, J Bierbach, A E Paz, S Kuschel, Martin Wunsche, Vinzenz Hilbert, U ZastrauAbstract:We report on the absolute sensitivity calibration of an extreme Ultraviolet (XUV) spectrometer system that is frequently employed to study emission from short-pulse laser experiments. The XUV spectrometer, consisting of a toroidal mirror and a transmission grating, was characterized at a synchrotron source in respect of the ratio of the detected to the incident photon flux at photon energies ranging from 15.5 eV to 99 eV. The absolute calibration allows the determination of the XUV photon number emitted by laser-based XUV Sources, e.g., high-harmonic generation from plasma surfaces or in gaseous media. We have demonstrated high-harmonic generation in gases and plasma surfaces providing 2.3 μW and μJ per harmonic using the respective generation mechanisms.
David Thilker - One of the best experts on this subject based on the ideXlab platform.
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revised catalog of galex Ultraviolet Sources i the all sky survey guvcat_ais
Astrophysical Journal Supplement Series, 2017Co-Authors: L Bianchi, Bernard Shiao, David ThilkerAbstract:The Galaxy Evolution Explorer (GALEX) imaged the sky in two Ultraviolet (UV) bands, far-UV (FUV, λ eff ~ 1528 A), and near-UV (NUV, λ eff ~ 2310 A), delivering the first comprehensive sky surveys at these wavelengths. The GALEX database contains FUV and NUV images, ~500 million source measurements and over 100,000 low-resolution UV spectra. The UV surveys are a unique resource for statistical studies of hot stellar objects, z 2 QSOs, star-forming galaxies, nebulae and the interstellar medium, and provide a roadmap for planning future UV instrumentation and follow-up observing programs. We present science-enhanced, "clean" catalogs of GALEX UV Sources, with useful tags to facilitate scientific investigations. The catalogs are an improved and expanded version of our previous catalogs of UV Sources (BCScat). With respect to BCScat, we have patched 640 fields for which the pipeline had improperly coadded non-overlapping observations, and we provide a version with a larger sky coverage (about 10%) by relaxing the restriction to the central area of the GALEX field to 11 diameter (GUVcat_AIS_fov055), as well as the cleaner, more restrictive version using only the 1° central portion of each field as in BCScat (GUVcat_AIS_fov050). We added new tags to facilitate selection and cleaning of statistical samples for science applications: we flag Sources within the footprint of extended objects (nearby galaxies, stellar clusters) so that these regions can be excluded for estimating source density. As in our previous catalogs, in GUVcat duplicate measurements of the same source are removed, so that each astrophysical object has only one entry. Such a unique-source catalog is needed to study the density and distributions of Sources, and to match UV Sources with catalogs at other wavelengths. The catalog includes all observations from the All-Sky Imaging Survey (AIS), the survey with the largest area coverage, with both FUV and NUV detectors exposed: over 28,700 fields, made up of a total of 57,000 observations ("visits"). The total area covered, when overlaps are removed and gaps are accounted for, is 24,790 square degrees for GUVcat_AIS_fov055 (GUVcat_AIS_fov055) and 22,125 square degrees for (GUVcat_AIS_fov050). The total numbers of "unique" AIS Sources (eliminating duplicate measurements) are 82,992,086 () and 69,772,677 (). The typical depth of the GUVcat_AIS catalog is FUV = 19.9, NUV = 20.8 AB mag.
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revised catalog of galex Ultraviolet Sources i the all sky survey guvcat_ais
arXiv: Astrophysics of Galaxies, 2017Co-Authors: L Bianchi, Bernard Shiao, David ThilkerAbstract:The Galaxy Evolution Explorer (GALEX) imaged the sky in two Ultraviolet (UV) bands, far-UV (FUV) and near-UV (NUV), delivering the first comprehensive sky surveys at these wavelengths. The GALEX database contains FUV and NUV images, 500~million source measurements and over 100,000 low-resolution UV spectra. [...] We present science-enhanced, clean catalogs of GALEX UV Sources, with useful tags to facilitate scientific investigations. The catalogs are an improved and expanded version of our previous catalogs of UV Sources (Bianchi et al. 2011, 2014: BCScat). With respect to BCScat, we have patched 640 fields for which the pipeline had improperly coadded non-overlapping observations, we provide a version with a larger sky coverage (about 10percent) [...]. We added new tags to facilitate selection and cleaning of statistical samples...: we flag Sources within the footprint of extended objects (nearby galaxies, stellar clusters) so that these regions can be excluded for estimating source density. As in our previous catalogs, in GUVcat duplicate measurements of the same source are removed.[...] Such unique-source catalog is needed to study density and distributions of Sources, and to match UV Sources with catalogs at other wavelengths. The catalog includes all observations from the All-Sky Imaging Survey (AIS), the survey with the largest area coverage, with both FUV and NUV detectors exposed: over 28,700 fields, made up of a total of 57,000 observations ("visits"). The total area covered, when overlaps are removed and gaps accounted for, is 24,790 (GUVcat_AIS_fov055) and 22,125 (GUVcat_AIS_fov050) square degrees. The total number of unique AIS Sources (eliminating duplicate measurements) is 82,992,086 (GUVcat_AIS_fov055) and 69,772,677 (GUVcat_AIS_fov050). The typical depth of the GUVcat_AIS catalog is FUV=19.9, NUV=20.8ABmag.
A. Tielens - One of the best experts on this subject based on the ideXlab platform.
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Ultrafast dynamics of correlation bands following XUV molecular photoionization
Nature Physics, 2020Co-Authors: Marius Hervé, V. Despré, P. Castellanos Nash, Vincent Loriot, Alexie Boyer, A. Scognamiglio, G. Karras, Richard Brédy, Eric Constant, A. TielensAbstract:Modern ultrashort X-ray/XUV (extreme Ultraviolet) Sources provide unique opportunities to investigate the primary reactions of matter upon energetic excitation. Understanding these processes in molecules on ultrafast timescales is required to improve bespoke high-energy radiation detectors, nanomedicine schemes or to study the molecular composition of interstellar media. However, current experiments struggle to provide a general framework because of the uniqueness and complexity of each system. Here we show the universal role of correlation bands—features created by electron correlation. This is done by studying ultrafast energy relaxation of size-scalable two-dimensional molecules following ionization by an ultrashort XUV pulse. We observed long lifetimes that nonlinearly increase with the number of valence electrons. A general law based on solid-like electron–phonon scattering is proposed, which explains both our results and previously reported measurements. This offers new opportunities in attosecond science and high-energy photophysics.
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Ultrafast dynamics of correlation bands following XUV molecular photoionization
Nature Physics, 2020Co-Authors: Marius Hervé, V. Despré, P. Castellanos Nash, Vincent Loriot, Alexie Boyer, A. Scognamiglio, G. Karras, Richard Brédy, Eric Constant, A. TielensAbstract:Modern ultrashort X-ray/XUV (extreme Ultraviolet) Sources provide unique opportunities to investigate the primary reactions of matter upon energetic excitation. Understanding these processes in molecules on ultrafast timescales is required to improve bespoke high-energy radiation detectors, nanomedicine schemes or to study the molecular composition of interstellar media. However, current experiments struggle to provide a general framework because of the uniqueness and complexity of each system. Here we show the universal role of correlation bands—features created by electron correlation. This is done by studying ultrafast energy relaxation of size-scalable two-dimensional molecules following ionization by an ultrashort XUV pulse. We observed long lifetimes that nonlinearly increase with the number of valence electrons. A general law based on solid-like electron–phonon scattering is proposed, which explains both our results and previously reported measurements. This offers new opportunities in attosecond science and high-energy photophysics. The size-dependent lifetimes observed in the ultrafast molecular relaxation dynamics of an entire class of polycyclic aromatic hydrocarbons can be explained by correlation bands and electron–phonon scattering, reminiscent of solid-state systems.
Duilia F. De Mello - One of the best experts on this subject based on the ideXlab platform.
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Near-Ultraviolet Sources in the Hubble Ultra Deep Field: The Catalog
The Astronomical Journal, 2009Co-Authors: Elysse N. Voyer, Duilia F. De Mello, Jonathan P. Gardner, Brian Siana, Cori Quirk, Harry I. TeplitzAbstract:The catalog from the first high-resolution U-band image of the Hubble Ultra Deep Field, taken with Hubble's Wide-Field Planetary Camera 2 through the F300W filter, is presented. We detect 96 U-band objects and compare and combine this catalog with a Great Observatories Origins Deep Survey B-selected catalog that provides B, V, i, and z photometry, spectral types, and photometric redshifts. We have also obtained far-Ultraviolet (FUV, 1614 A) data with Hubble's Advanced Camera for Surveys Solar Blind Channel (ACS/SBC) and with GALEX. We detected 31 Sources with ACS/SBC, 28 with GALEX/FUV, and 45 with GALEX/NUV. The methods of observations, image processing, object identification, catalog preparation, and catalog matching are presented.
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near Ultraviolet Sources in the great observatories origins deep survey fields
The Astronomical Journal, 2006Co-Authors: Duilia F. De Mello, Tomas Dahlen, Jonathan P. Gardner, N A GroginAbstract:We present an Ultraviolet-selected sample of 268 objects in the two fields of the Great Observatories Origins Deep Survey (GOODS). We used the parallel observations taken with the Wide Field Planetary Camera 2 in the U band (F300W), which covered 88% of the GOODS fields, to identify Sources and selected only objects with GOODS Advanced Camera for Surveys counterparts. Spectroscopic redshifts for 95 of these Sources are available, and we have used the multiwavelength GOODS data to estimate photometric redshifts for the others. Most of the objects have redshifts 0.2 < z < 0.8. We used the spectral types obtained by photometric redshift fitting to identify starburst galaxies. We have also visually checked all objects and looked for tidal effects and nearby companions. We find that (1) 45% of the UV-selected galaxies are starbursts, (2) nearly 75% of the starbursts have tidal tails or show some peculiarity typical of interactions or mergers, and (3) ~50% have companions within an area of 5'' × 5''. The UV-selected sample has an average rest-frame MB = -19.9 ± 0.1. The bluest objects in the sample (U - B < 0.2 and B - V < 0.1) are at 1.1 < z < 1.9 and have peculiar morphologies that resemble either tadpoles, chains, or double-clump galaxies. Starbursts with tadpole or clump morphologies at z = 0.8-1.3 have sizes comparable to Lyman break galaxies and compact UV-luminous galaxies.
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The Nature of Near Ultraviolet Sources in the GOODS Fields
Proceedings of the International Astronomical Union, 2006Co-Authors: Duilia F. De Mello, Tomas Dahlen, Jonathan P. GardnerAbstract:AbstractWe present the latest results of the survey searching for the nature of UV-selected galaxies in the Great Observatories Origins Deep Survey fields. By searching for UV-bright galaxies at intermediate redshifts (z ~ 1) we aim at understanding the nature of star-forming galaxies and their counterparts at higher-z, the so-called Lyman Break Galaxies.
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near Ultraviolet Sources in the great observatories origins deep survey fields
arXiv: Astrophysics, 2006Co-Authors: Duilia F. De Mello, Tomas Dahlen, Jonathan P. Gardner, N A GroginAbstract:We present an Ultraviolet (UV) selected sample of 268 objects in the two fields of the Great Observatories Origins Deep Survey (GOODS). We used the parallel observations taken with WFPC2 in the U--band (F300W) which covered 88% of the GOODS fields to identify Sources and selected only objects with GOODS/ACS counterparts. Spectroscopic redshifts for 95 of these Sources are available and we have used the multiwavelength GOODS data to estimate photometric redshifts for the others. Most of the objects are between 0.2
