# FS-FLASH-O

 2018-05-1415:17 [PUBDB-2018-01956] Journal Article et al Time-resolved inner-shell photoelectron spectroscopy: From a bound molecule to an isolated atom Physical review / A 97(4), 043429 (2018) [10.1103/PhysRevA.97.043429]   Due to its element and site specificity, inner-shell photoelectron spectroscopy is a widely used technique to probe the chemical structure of matter. Here, we show that time-resolved inner-shell photoelectron spectroscopy can be employed to observe ultrafast chemical reactions and the electronic response to the nuclear motion with high sensitivity [...] Fulltext: PNG; OpenAccess: PDF PDF (PDFA); 2018-05-1415:05 [PUBDB-2018-01953] Journal Article et al Time-resolved ion imaging at free-electron lasers using TimepixCam Journal of synchrotron radiation 25(2), 336 - 345 (2018) [10.1107/S1600577517018306]   The application of a novel fast optical-imaging camera, TimepixCam, to molecular photoionization experiments using the velocity-map imaging technique at a free-electron laser is described. TimepixCam is a 256 × 256 pixel CMOS camera that is able to detect and time-stamp ion hits with 20 ns timing resolution, thus making it possible to record ion momentum images for all fragment ions simultaneously and avoiding the need to gate the detector on a single fragment. [...] Restricted: PDF PDF (PDFA); 2018-01-0513:44 [PUBDB-2018-00199] Journal Article et al Photodissociation of Aligned $\mathrm{CH_3I}$ and $\mathrm{C_{6}H_{3}F_{2}I}$ Molecules Probed with Time-Resolved Coulomb Explosion Imaging by Site-Selective XUV Ionization Structural dynamics 5(1), 014301 - (2018) [10.1063/1.4998648]   We explore time-resolved Coulomb explosion induced by intense, extreme ultraviolet (XUV) femtosecond pulses from a free-electron laser as a method to image photo-induced molecular dynamics in two molecules, iodomethane and 2,6-difluoroiodobenzene. At an excitation wavelength of 267 nm, the dominant reaction pathway in both molecules is neutral dissociation via cleavage of the carbon–iodine bond. [...] Fulltext: PNG; OpenAccess: PDF PDF (PDFA); 2018-01-0316:49 [PUBDB-2018-00094] Journal Article/Contribution to a conference proceedings/Contribution to a book Yurkov, M. Frequency Doubler and Two-Color Mode of Operation at Free Electron Laser FLASH2 Proc. SPIE, 2017. - ISBN - doi:10.1117/12.2265584Advances in X-ray Free-Electron Lasers Instrumentation IV, PraguePrague, Czech Republic, 24 Apr 2017 - 27 Apr 2017 Proceedings of SPIE 10237, 1023710 (2017) [10.1117/12.2265584] special issue: "Advances in X-ray Free-Electron Lasers Instrumentation IV"   We report on the results of the first operation of a frequency doubler at FLASH2. The scheme uses the feature of the variable gap of the undulator. [...] OpenAccess: 1023710 - PDF PDF (PDFA); 10237-35_Yurkov_Doubler-SPIE - PDF PDF (PDFA); 2017-12-2214:02 [PUBDB-2017-14060] Journal Article et al Experimental study of EUV mirror radiation damage resistance under long-term free-electron laser exposures below the single-shot damage threshold Journal of synchrotron radiation 25(1), 77 - 84 (2018) [10.1107/S1600577517017362]   The durability of grazing- and normal-incidence optical coatings has been experimentally assessed under free-electron laser irradiation at various numbers of pulses up to 16 million shots and various fluence levels below 10% of the single-shot damage threshold. The experiment was performed at FLASH, the Free-electron LASer in Hamburg, using 13.5 nm extreme UV (EUV) radiation with 100 fs pulse duration. [...] OpenAccess: PDF PDF (PDFA); 2017-12-2015:10 [PUBDB-2017-13877] Journal Article et al Observation of Reverse Saturable Absorption of an X-ray Laser Physical review letters 119(7), 075002 (2017) [10.1103/PhysRevLett.119.075002]   A nonlinear absorber in which the excited state absorption is larger than the ground state can undergo a process called reverse saturable absorption. It is a well-known phenomenon in laser physics in the optical regime, but is more difficult to generate in the x-ray regime, where fast nonradiative core electron transitions typically dominate the population kinetics during light matter interactions [...] OpenAccess: PDF PDF (PDFA); 2017-12-1911:10 [PUBDB-2017-13688] Journal Article/Contribution to a conference proceedings/Contribution to a book et al A soft x-ray split-and-delay unit for FLASH II : [Proceedings] - , 2017. - doi:10.1117/12.2265708Advances in X-ray Free-Electron Lasers Instrumentation IV, PraguePrague, Czech Republic, 24 Apr 2017 - 27 Apr 2017 Proceedings of SPIE 10237, 1023712 (2017) [10.1117/12.2265708]   For the soft x-ray free-electron laser FLASH II at DESY in Hamburg a new split-and-delay unit (SDU) is built for photon energies in the range of 30 eV < hν < 1500 eV with an option to expand this range to hν = 2500 eV. The SDU is based on wavefront beam splitting at grazing incidence angles. [...] OpenAccess: PDF PDF (PDFA); 2017-12-1818:46 [PUBDB-2017-13675] Journal Article et al Non-invasive online wavelength measurements at FLASH2 and present benchmark Journal of synchrotron radiation 25(1), 3 - 15 (2018) [10.1107/S1600577517013893] special issue: "PhotonDiag2017 Workshop special issue"   At FLASH2, the free-electron laser radiation wavelength is routinely measured by an online spectrometer based on photoionization of gas targets. Photoelectrons are detected with time-of-flight spectrometers and the wavelength is determined by means of well known binding energies of the target species. [...] OpenAccess: PDF PDF (PDFA); 2017-12-1811:00 [PUBDB-2017-13615] Contribution to a conference proceedings et al Status of the Soft X-Ray Free Electron Laser FLASH 8th International Particle Accelerator Conference, IPAC2017, CopenhagenCopenhagen, Denmark, 14 May 2017 - 19 May 2017 JACoW, Geneva, Switzerland 3 pp. (2017) [10.18429/JACoW-IPAC2017-WEPAB025]   The superconducting free-electron laser user facility FLASH at DESY in Hamburg, routinely produces several thousand photon pulses per second. The operational parameters cover a wavelength range from 90 nm down to 4 nm with pulse energies from several $\mu$J up to 1 mJ and with pulse durations of several hundred fs down to a few fs. [...] OpenAccess: PDF PDF (PDFA); External link: Fulltext 2017-12-1810:52 [PUBDB-2017-13612] Poster et al Status of the Soft X-Ray Free Electron Laser FLASH 8th International Particle Accelerator Conference, IPAC2017, CopenhagenCopenhagen, Denmark, 14 May 2017 - 19 May 2017   The superconducting free-electron laser user facility FLASH at DESY in Hamburg, routinely produces several thousand photon pulses per second. The operational parameters cover a wavelength range from 90 nm down to 4 nm with pulse energies from several $\mu$J up to 1 mJ and with pulse durations of several hundred fs down to a few fs. [...] OpenAccess: PDF PDF (PDFA);