CFEL-DESYT

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2019-03-20
08:43
Embargoed OpenAccess [PUBDB-2019-01624] Journal Article

Probing photodissociation dynamics using ring polymer molecular dynamics
The performance of the ring polymer molecular dynamics (RPMD) approach to simulate typical photodissociation processes is assessed. The correct description of photodissociation requires the calculation of correlation functions or expectation values associated with non-equilibrium initial conditions, which was shown to be possible with RPMD very recently [J. [...]
Published on 2019-03-18. Available in OpenAccess from 2020-03-18.: Download fulltextPDF Download fulltextPDF (PDFA);
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2019-03-19
10:24
OpenAccess [PUBDB-2019-01603] Journal Article

Time-resolved x-ray/optical pump-probe simulations on $\mathrm{N_2}$ molecules
Structural dynamics 6(2), 024101 () [10.1063/1.5053995]  GO
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 [...]
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2019-02-21
08:34
OpenAccess [PUBDB-2019-01191] Journal Article

Time-dependent QED approach to x-ray nonlinear Compton scattering
Motivated by a recent experiment [Fuchs et al., Nat. Phys [...]
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2019-02-20
13:59
OpenAccess [PUBDB-2019-01181] Journal Article
et al
X-ray induced damage of B$_4$C-coated bilayer materials under various irradiation conditions
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 [...]
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2019-02-04
13:49
OpenAccess [PUBDB-2019-00936] Journal Article
et al
Femtosecond phase-transition in hard x-ray excited bismuth
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 [...]
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2019-02-04
13:38
Embargoed OpenAccess [PUBDB-2019-00935] Journal Article
et al
Simulated XUV photoelectron spectra of THz-pumped liquid water
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.: Download fulltextPDF Download fulltextPDF (PDFA);
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2018-12-20
09:22
OpenAccess [PUBDB-2018-05775] Journal Article

Infrared-laser-pulse-enhanced ultrafast fragmentation of $N_2^{2+}$ following Auger decay: Mixed quantum-classical simulations
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 [...]
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2018-12-05
09:40
OpenAccess [PUBDB-2018-05211] Journal Article
et al
Ultrafast nuclear dynamics in the doubly-core-ionized water molecule observed via Auger spectroscopy
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 [...]
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2018-12-05
09:31
OpenAccess [PUBDB-2018-05209] Journal Article

Theory of x-ray scattering from laser-driven electronic systems
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 [...]
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2018-10-11
09:55
OpenAccess [PUBDB-2018-03750] Journal Article
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Relativistic and resonant effects in the ionization of heavy atoms by ultra-intense hard X-rays
An accurate description of the interaction of intense hard X-ray pulses with heavy atoms,which is crucial for many applications of free-electron lasers, represents a hitherto unresolvedchallenge for theory because of the enormous number of electronic configurations andrelativistic effects, which need to be taken into account. Here we report results on multipleionization of xenon atoms by ultra-intense (about 1019W/cm2) femtosecond X-ray pulses atphoton energies from 5.5 to 8.3 keV and present a theoretical model capable of reproducingthe experimental data in the entire energy range. [...]
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