AMO science at the FLASH and European XFEL free-electron laser facilities

Feldhaus, J.; Krikunova, Maria; Meyer, Michael; Möller, T.; Moshammer, R.; Rudenko, Artem; Tschentscher, Th.; Ullrich, J.

doi:10.1088/0953-4075/46/16/164002

Cited by 98 publications

(82 citation statements)

References 111 publications

(151 reference statements)

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“…For this reason, we assume that ω L = N osc ω = 20 eV and the time-averaged intensity is I = 10 20 W/cm 2 (as it has been chosen for instance in Ref. [49]); in other words, we consider parameters which are experimentally available [69][70][71].…”

Section: A Pulse Shapementioning

confidence: 99%

Supercontinuum in ionization by relativistically intense and short laser pulses: Ionization without interference and its time analysis

Krajewska

Kamiński

2016

Phys. Rev. A

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Ionization by relativistically intense laser pulses of finite duration is considered in the framework of strongfield quantum electrodynamics. We show that the resulting ionization spectra change their behavior from the interference-dominated oscillatory pattern to the interference-free smooth supercontinuum, the latter being the main focus of this paper. More specifically, when studying the energy distributions of photoelectrons ionized by circularly polarized and short pulses, we observe the appearance of broad structures lacking the interference patterns. These supercontinua extend over hundreds of driving photon energies, thus corresponding to high-order nonlinear processes. Their positions on the electron energy scale can be controlled by changing the pulse duration. The corresponding polar-angle distributions show asymmetries which are attributed to the radiation pressure experienced by photoelectrons. Moreover, our time analysis shows that the electrons comprising the supercontinuum can form pulses of short duration. While we present the fully numerical results, their interpretation is based on the saddle-point approximation for the ionization probability amplitude.

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Section: A Pulse Shapementioning

confidence: 99%

Supercontinuum in ionization by relativistically intense and short laser pulses: Ionization without interference and its time analysis

Krajewska

Kamiński

2016

Phys. Rev. A

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“…A series of decay processes, a socalled decay cascade, can occur if the hole is formed in a deep inner shell [1][2][3][4][5]. The interaction with x rays becomes rather complex when the sample is exposed to the unprecedentedly high fluence generated by x-ray free-electron lasers (XFELs) [6][7][8][9]. Beyond the one-photon saturation fluence, which is the inverse of the single-photon ionization cross section [10], a single atom can absorb more than one photon sequentially after or during decay cascades, and then it becomes a highly charged ion.…”

Section: Introductionmentioning

confidence: 99%

Interplay between relativistic energy corrections and resonant excitations in x-ray multiphoton ionization dynamics of Xe atoms

2017

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In this paper, we theoretically study x-ray multiphoton ionization dynamics of heavy atoms taking into account relativistic and resonance effects. When an atom is exposed to an intense x-ray pulse generated by an x-ray free-electron laser (XFEL), it is ionized to a highly charged ion via a sequence of single-photon ionization and accompanying relaxation processes, and its final charge state is limited by the last ionic state that can be ionized by a single-photon ionization. If x-ray multiphoton ionization involves deep inner-shell electrons in heavy atoms, energy shifts by relativistic effects play an important role in ionization dynamics, as pointed out in Phys. Rev. Lett. 110, 173005 (2013). On the other hand, if the x-ray beam has a broad energy bandwidth, the high-intensity x-ray pulse can drive resonant photoexcitations for a broad range of ionic states and ionize even beyond the direct one-photon ionization limit, as first proposed in Nat. Photon. 6, 858 (2012). To investigate both relativistic and resonance effects, we extend the XATOM toolkit to incorporate relativistic energy corrections and resonant excitations in x-ray multiphoton ionization dynamics calculations. Charge-state distributions are calculated for Xe atoms interacting with intense XFEL pulses at a photon energy of 1.5 keV and 5.5 keV, respectively. For both photon energies, we demonstrate that the role of resonant excitations in ionization dynamics is altered due to significant shifts of orbital energy levels by relativistic effects. Therefore, it is necessary to take into account both effects to accurately simulate multiphoton multiple ionization dynamics at high x-ray intensity.

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“…In the last decade, free-electron laser facilities operating in the XUV and X-ray regimes have become available for scientific investigations [1][2][3]. These facilities have opened up the research area of laser-matter interactions in intense high-frequency fields.…”

Section: Introductionmentioning

confidence: 99%

Time-dependentR-matrix theory applied to two-photon double ionization of He

Hart

2014

Phys. Rev. A

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We introduce a time-dependent R-matrix theory generalised to describe double ionization processes. The method is used to investigate two-photon double ionization of He by intense XUV laser radiation. We combine a detailed B-spline-based wavefunction description in a extended inner region with a single-electron outer region containing channels representing both single ionization and double ionization. A comparison of wavefunction densities for different box sizes demonstrates that the flow between the two regions is described with excellent accuracy. The obtained two-photon double ionization cross sections are in excellent agreement with other cross sections available. Compared to calculations fully contained within a finite inner region, the present calculations can be propagated over the time it takes the slowest electron to reach the boundary.PACS numbers: 32.80. Rm, 32.80.Fb

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AMO science at the FLASH and European XFEL free-electron laser facilities

Cited by 98 publications

References 111 publications

Supercontinuum in ionization by relativistically intense and short laser pulses: Ionization without interference and its time analysis

Supercontinuum in ionization by relativistically intense and short laser pulses: Ionization without interference and its time analysis

Interplay between relativistic energy corrections and resonant excitations in x-ray multiphoton ionization dynamics of Xe atoms

Time-dependentR-matrix theory applied to two-photon double ionization of He

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