2018-8-3, Sauppe, Mario, Rompotis, Dimitrios, Erk, Benjamin, Bari, Sadia, Bischoff, Tobias, Boll, Rebecca, Bomme, Cédric, Bostedt, Christoph, Dörner, Simon, Düsterer, Stefan, Feigl, Torsten, Flückiger, Leonie, Gorkhover, Tais, Kolatzki, Katharina, Langbehn, Bruno, Monserud, Nils, Müller, Erland, Müller, Jan P., Passow, Christopher, Ramm, Daniel, Rolles, Daniel, Schubert, Kaja, Schwob, Lucas, Senfftleben, Björn, Treusch, Rolf, Ulmer, Anatoli, Weigelt, Holger, Zimbalski, Jannis, Zimmermann, Julian, Möller, Thomas, Rupp, Daniela

Extreme ultraviolet (XUV) and X-ray free-electron lasers enable new scientific opportunities. Their ultra-intense coherent femtosecond pulses give unprecedented access to the structure of undepositable nanoscale objects and to transient states of highly excited matter. In order to probe the ultrafast complex light-induced dynamics on the relevant time scales, the multi-purpose end-station CAMP at the free-electron laser FLASH has been complemented by the novel multilayer-mirror-based split-and-delay unit DESC (DElay Stage for CAMP) for time-resolved experiments. XUV double-pulses with delays adjustable from zero femtoseconds up to 650 picoseconds are generated by reflecting under near-normal incidence, exceeding the time range accessible with existing XUV split-and-delay units. Procedures to establish temporal and spatial overlap of the two pulses in CAMP are presented, with emphasis on the optimization of the spatial overlap at long time-delays via time-dependent features, for example in ion spectra of atomic clusters.

2020, Rupp, Daniela, Flückiger, Leonie, Adolph, Marcus, Colombo, Alessandro, Gorkhover, Tais, Harmand, Marion, Krikunova, Maria, Müller, Jan Philippe, Oelze, Tim, Ovcharenko, Yevheniy, Richter, Maria, Sauppe, Mario, Schorb, Sebastian, Treusch, Rolf, Wolter, David, Bostedt, Christoph, Möller, Thomas

We have recorded the diffraction patterns from individual xenon clusters irradiated with intense extreme ultraviolet pulses to investigate the influence of light-induced electronic changes on the scattering response. The clusters were irradiated with short wavelength pulses in the wavelength regime of different 4d inner-shell resonances of neutral and ionic xenon, resulting in distinctly different optical properties from areas in the clusters with lower or higher charge states. The data show the emergence of a transient structure with a spatial extension of tens of nanometers within the otherwise homogeneous sample. Simulations indicate that ionization and nanoplasma formation result in a light-induced outer shell in the cluster with a strongly altered refractive index. The presented resonant scattering approach enables imaging of ultrafast electron dynamics on their natural timescale.