# FS-CFEL-3

 2019-03-1910:24 [PUBDB-2019-01603] Journal Article Santra, R. Time-resolved x-ray/optical pump-probe simulations on $\mathrm{N_2}$ molecules Structural dynamics 6(2), 024101 (2019) [10.1063/1.5053995]   The dynamics of $N_2^{2+}$ dications after x-ray-induced Auger decay and their probing with a delayed infrared probe pulse are theoretically investigated based on a quantum-mechanical model including all relevant electronic states for which wave-packet calculations on ab-initio potential energy curves are performed. Our results demonstrate that the $N_2^{2+}$ yield modulated by the delay of the probe pulse contains dynamical information on the wave-packet evolution in the quasi-bound final electronic states [...] OpenAccess: PDF PDF (PDFA); 2019-02-2108:34 [PUBDB-2019-01191] Journal Article Santra, R. Time-dependent QED approach to x-ray nonlinear Compton scattering Physical review / A 99(2), 022120 (2019) [10.1103/PhysRevA.99.022120]   Motivated by a recent experiment [Fuchs et al., Nat. Phys [...] OpenAccess: PDF PDF (PDFA); 2019-02-2013:59 [PUBDB-2019-01181] Journal Article et al X-ray induced damage of B$_4$C-coated bilayer materials under various irradiation conditions Scientific reports 9(1), 2029 (2019) [10.1038/s41598-019-38556-0]   In this report, we analyse X-ray induced damage of B$_4$C-coated bilayer materials under various irradiation geometries, following the conditions of our experiment performed at the free-electron-laser facility SACLA. We start with the discussion of structural damage in solids and damage threshold doses for the experimental system components: B$_4$C, SiC, Mo and Si [...] OpenAccess: PDF PDF (PDFA); 2019-02-0413:49 [PUBDB-2019-00936] Journal Article et al Femtosecond phase-transition in hard x-ray excited bismuth Scientific reports 9(1), 602 (2019) [10.1038/s41598-018-36216-3]   The evolution of bismuth crystal structure upon excitation of its $A_{1g}$ phonon has been intensely studied with short pulse optical lasers. Here we present the first-time observation of a hard x-ray induced ultrafast phase transition in a bismuth single crystal at high intensities $(~10^{14} W/cm^2 ).$ The lattice evolution was followed using a recently demonstrated x-ray single-shot probing setup [...] OpenAccess: PDF PDF (PDFA); 2019-02-0413:38 [PUBDB-2019-00935] Journal Article et al Simulated XUV photoelectron spectra of THz-pumped liquid water The journal of chemical physics 150(4), 044505 (2019) [10.1063/1.5054272]   Highly intense, sub-picosecond terahertz (THz) pulses can be used to induce ultrafast temperature jumps (T-jumps) in liquid water. A supercritical state of gas-like water with liquid density is established, and the accompanying structural changes are expected to give rise to time-dependent chemical shifts. [...] Published on 2019-01-29. Available in OpenAccess from 2020-01-29.: PDF PDF (PDFA); 2019-01-3015:23 [PUBDB-2019-00875] Journal Article et al Roadmap of ultrafast x-ray atomic and molecular physics Journal of physics / B 51(3), 032003 (2018) [10.1088/1361-6455/aa9735]   X-ray free-electron lasers (XFELs) and table-top sources of x-rays based upon high harmonic generation (HHG) have revolutionized the field of ultrafast x-ray atomic and molecular physics, largely due to an explosive growth in capabilities in the past decade. XFELs now provide unprecedented intensity (1020 W cm−2) of x-rays at wavelengths down to ~1 Ångstrom, and HHG provides unprecedented time resolution (~50 attoseconds) and a correspondingly large coherent bandwidth at longer wavelengths [...] OpenAccess: PDF PDF (PDFA); 2018-12-2009:22 [PUBDB-2018-05775] Journal Article Welsch, R. Infrared-laser-pulse-enhanced ultrafast fragmentation of $N_2^{2+}$ following Auger decay: Mixed quantum-classical simulations Physical review / A 98(6), 063421 (2018) [10.1103/PhysRevA.98.063421]   We employ mixed quantum-classical molecular dynamics simulations to investigate the fragmentation of $N_2$ molecules after core-level photoionization by an x-ray laser, subsequent Auger decay, and followed by a femtosecond IR pulse that interacts with $N_2^{2+}$. The delayed IR pulse couples the dissociative electronic states of $N_2^{2+}$ with electronic states that can support long-lived vibrational resonances [...] OpenAccess: PDF PDF (PDFA); 2018-12-0509:40 [PUBDB-2018-05211] Journal Article et al Ultrafast nuclear dynamics in the doubly-core-ionized water molecule observed via Auger spectroscopy Physical review / A 98(6), 063403 (2018) [10.1103/PhysRevA.98.063403]   We present a combined experimental and theoretical study of the Auger-emission spectrum following double core ionization and excitation of gas-phase water molecules with hard-x-ray synchrotron radiation above the O $K^{−2}$ threshold. We observe an indication of ultrafast proton motion occurring within the 1.5 fs lifetime of the double-core-hole (DCH) states in water [...] OpenAccess: PDF PDF (PDFA); 2018-12-0509:31 [PUBDB-2018-05209] Journal Article Santra, R. Theory of x-ray scattering from laser-driven electronic systems Physical review / B 98(22), 224302 (2018) [10.1103/PhysRevB.98.224302]   We describe, within the framework of quantum electrodynamics, an interaction between a nonresonant hard x-ray pulse and an electronic system in the presence of a temporally periodic laser field driving electron dynamics in this system. We apply Floquet theory to describe the laser-driven electronic system, and then obtain the scattering probability of an arbitrary nonresonant x-ray pulse from such a system employing the density-matrix formalism [...] OpenAccess: PDF PDF (PDFA); 2018-10-1710:44 [PUBDB-2018-03818] Poster et al Ultrafast Demagnetization by Extreme Ultraviolet Light German Conference for Research with Synchrotron Radiation, Neutrons and Ion Beams at Large Facilities, SNI, MünchenMünchen, Germany, 17 Sep 2018 - 19 Sep 2018 Free-electron lasers (FELs) enable the study of dynamics in matter on combined femtosecond time and nanometer length scales [1]. One of the most intriguing topics within contemporary research on magnetism, ultrafast near-infrared (IR) laser-induced demagnetization [2,3], has greatly benefited from the advent of FELs [4] as it was shown that optically generated superdiffusive spin currents [5] contribute to that phenomenon [6]. [...]