Suchergebnisse

The role of the nuclear degrees of freedom in nonlinear two-photon single ionization of H2 molecules interacting with short and intense vacuum ultraviolet pulses is investigated, both experimentally and theoretically, by selecting single resonant vibronic intermediate neutral states. This high selectivity relies on the narrow bandwidth and tunability of the pulses generated at the FERMI free-electron laser. A sustained enhancement of dissociative ionization, which even exceeds nondissociative ionization, is observed and controlled as one selects progressively higher vibronic states. With the help of ab initio calculations for increasing pulse durations, the photoelectron and ion energy spectra obtained with velocity map imaging allow us to identify new photoionization pathways. With pulses of the order of 100 fs, the experiment probes a timescale that lies between that of ultrafast dynamical processes and that of steady state excitations ; This research was supported by "Investissements d'Avenir" LabEx PALM (ANR-10-LABX-0039-PALM) and EquipEx ATTOLAB (ANR-11-EQPX-0005- ATTOLAB), as well as by the EU-H2020 Laserlab- Europe 654148. This work is supported by the ERC advanced Grant No. 290853—XCHEM—within the seventh framework program of the European Union. We also acknowledge the financial support from the MINECO Project No. FIS2016-77889-R and the European COST Action XLIC CM1204 and the computer time from the CCC-UAM and Marenostrum Supercomputer. A. P. acknowledges a Ramón y Cajal contract from the Ministerio de Economía y Competitividad (Spain). F. M. acknowledges support from the "Severo Ochoa" Program for Centres of Excellence in R&D (MINECO, Grant No. SEV-2016-0686) and the "María de Maeztu" Program for Units of Excellence in R&D (MDM-2014- 0377). D. D. and M. H. acknowledge support by Institut de Physique (CNRS). M. M. acknowledges support by the Deutsche Forschungsgemeinschaft (DFG) under Grants No. SFB925/A3 and CUI, No. DFG-EXC1074. We gratefully acknowledge the members of the FERMI team at Elettra-Sincrotrone Trieste whose work made this experiment possible

The toolbox for imaging molecules is well-equipped today. Some techniques visualize the geometrical structure, others the electron density or electron orbitals. Molecules are many-body systems for which the correlation between the constituents is decisive and the spatial and the momentum distribution of one electron depends on those of the other electrons and the nuclei. Such correlations have escaped direct observation by imaging techniques so far. Here, we implement an imaging scheme which visualizes correlations between electrons by coincident detection of the reaction fragments after high energy photofragmentation. With this technique, we examine the H2two-electron wave function in which electron-electron correlation beyond the mean-field level is prominent. We visualize the dependence of the wave function on the internuclear distance. High energy photoelectrons are shown to be a powerful tool for molecular imaging. Our study paves the way for future time resolved correlation imaging at FELs and laser based X-ray sources ; This work was funded by the Deutsche Forschungsgemeinschaft, the BMBF, the European Research Council under the European Union Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement 290853 XCHEM, the MINECO projects FIS2013-42002-R and FIS2016-77889-R, and the European COST Action XLIC CM1204. All calculations were performed at the CCC-UAM and Mare Nostrum Supercomputer Centers. We are grateful to the staff of PETRA III for excellent support during the beam time. K.M. and M.M. would like to thank the DFG for support via SFB925/A3. A.K. and V.S. thank the Wilhelm und Else Heraeus-Foundation for support. J.L. would like to thank the DFG for support. S.K. acknowledges support from the European Cluster of Advanced Laser Light Sources (EUCALL) project which has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 654220. T.W. was supported by the U.S. Department of Energy Basic Energy Sciences under Contract No. DE-AC02-05CH11231. A.P. acknowledges a Ramón y Cajal contract from the Ministerio de Economa y Competitividad

The Javalambre Photometric Local Universe Survey (J-PLUS) is an ongoing 12-band photometric optical survey, observing thousands of square degrees of the Northern Hemisphere from the dedicated JAST/T80 telescope at the Observatorio Astrofísico de Javalambre (OAJ). The T80Cam is a camera with a field of view of 2 deg 2 mounted on a telescope with a diameter of 83 cm, and is equipped with a unique system of filters spanning the entire optical range (3500-10 000 Å). This filter system is a combination of broad-, medium-, and narrow-band filters, optimally designed to extract the rest-frame spectral features (the 3700-4000 Å Balmer break region, Hδ, Ca H+K, the G band, and the Mg b and Ca triplets) that are key to characterizing stellar types and delivering a low-resolution photospectrum for each pixel of the observed sky. With a typical depth of AB ∼21.25 mag per band, this filter set thus allows for an unbiased and accurate characterization of the stellar population in our Galaxy, it provides an unprecedented 2D photospectral information for all resolved galaxies in the local Universe, as well as accurate photo-z estimates (at the δ z/(1 + z)∼0.005-0.03 precision level) for moderately bright (up to r∼20 mag) extragalactic sources. While some narrow-band filters are designed for the study of particular emission features ([O II]/λ3727, Hα/λ6563) up to z< 0.017, they also provide well-defined windows for the analysis of other emission lines at higher redshifts. As a result, J-PLUS has the potential to contribute to a wide range of fields in Astrophysics, both in the nearby Universe (Milky Way structure, globular clusters, 2D IFU-like studies, stellar populations of nearby and moderate-redshift galaxies, clusters of galaxies) and at high redshifts (emission-line galaxies at z≈0.77, 2.2, and 4.4, quasi-stellar objects, etc.). With this paper, we release the first ∼1000 deg 2 of J-PLUS data, containing about 4.3 million stars and 3.0 million galaxies at r< 21 mag. With a goal of 8500 deg 2 for the total J-PLUS footprint, these numbers are expected to rise to about 35 million stars and 24 million galaxies by the end of the survey. © ESO 2019. ; Funding for the J-PLUS Project has been provided by the Governments of Spain and Aragon through the Fondo de Inversiones de Teruel, by the Spanish Ministry of Economy and Competitiveness (MINECO; under grants AYA2012-30789, AYA2013-40611-P, AYA2015-66211-C2-1-P, AYA2015-66211-C2-2, AYA2016-77846-P, AYA2016-77237-C3-1-P, AYA2016-75931-C2-1-P, AYA2017-86274-P, AGAURgrantSGR-661/2017, andICTS-2009-14), byFAPERJ the Government of Aragon, through the Grupo de Investigacion E16_17R, and by European FEDER funding (FCDD10-4E-867, FCDD13-4E-2685). Further support has been provided by the Ramon y Cajal programmes RYC-2016-20254, RYC-2011-08262 and RYC-2011-08529. This research has made use of the Spanish Virtual Observatory (http://svo.cab.inta-csic.es) supported from the Spanish MINECO through grant AYA2014-55216. We also acknowledge Spanish CSIC (I-COOP+ 2016 program) through grant COOPB20263. The Brazilian agencies FAPESP and the National Observatory of Brazil have also contributed to this project. We acknowledge financial support from the Fundacao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro - FAPERJ (fellowship Nota 10, PDR-10), from CNPq through BP grant 312307/2015-2 and Universal Grants 459553/20143, PQ 302037/2015-2, and PDE 200289/2017-9), FINEP grants REF. 1217/13 -01.13.0279.00 and REF 0859/10 -01.10.0663.00, from FAPERJ grant E-26/202.835/2016, and CAPES (Science without Borders program, Young Talent Fellowship, BJT) through grants A062/2013 and CAPES-PNPD 2940/2011. The FAPESP grants no. 2015/12745-6, 2014/11338-5, 2014/07684-5, 2013/04582-4 and 2009/54202-8 are also acknowledged. Finally, the authors acknowledge partial support from grant PHY 14-30152; Physics Frontier Center/JINA Center for the Evolution of the Elements (JINA-CEE), awarded by the US National Science Foundation. ; Peer Reviewed