<i>xcalib</i>: a focal spot calibrator for intense X-ray free-electron laser pulses based on the charge state distributions of light atoms

Toyota, Koudai; Jurek, Zoltán; Son, Sang−Kil; Fukuzawa, H.; Ueda, Kiyoshi; Berrah, N.; Rudek, Benedikt; Rolles, Daniel; Rudenko, Artem; Santra, Robin

doi:10.1107/s1600577519003564

Cited by 18 publications

(37 citation statements)

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“…To account for the spatial distribution of the x-ray fluence in the interaction region, the simulation results were integrated over the spatial profile of the pulse, which was determined using the measured charge state distributions (CSDs) of argon atoms as described in Ref. [34]. Further details of the experimental setup and simulation procedures are described in the Methods section of Ref.…”

mentioning

confidence: 99%

Pulse Energy and Pulse Duration Effects in the Ionization and Fragmentation of Iodomethane by Ultraintense Hard X Rays

Inhester

Robatjazi

et al. 2021

Phys. Rev. Lett.

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The interaction of intense femtosecond x-ray pulses with molecules sensitively depends on the interplay between multiple photoabsorptions, Auger decay, charge rearrangement, and nuclear motion. Here, we report on a combined experimental and theoretical study of the ionization and fragmentation of iodomethane (CH 3 I) by ultraintense (∼10 19 W=cm 2 ) x-ray pulses at 8.3 keV, demonstrating how these dynamics depend on the x-ray pulse energy and duration. We show that the timing of multiple ionization steps leading to a particular reaction product and, thus, the product's final kinetic energy, is determined by the pulse duration rather than the pulse energy or intensity. While the overall degree of ionization is mainly defined by the pulse energy, our measurement reveals that the yield of the fragments with the highest charge states is enhanced for short pulse durations, in contrast to earlier observations for atoms and small molecules in the soft x-ray domain. We attribute this effect to a decreased charge transfer efficiency at larger internuclear separations, which are reached during longer pulses.

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confidence: 99%

Pulse Energy and Pulse Duration Effects in the Ionization and Fragmentation of Iodomethane by Ultraintense Hard X Rays

Inhester

Robatjazi

et al. 2021

Phys. Rev. Lett.

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“…The fluence is fixed at 1.0×10 11 ph/μm 2 , and we assume that atoms experience the same fluence throughout the supercell. When an XFEL pulse is focused onto a target, the x-ray fluence value has a spatially nonuniform distribution in the focal spot, demanding volume integration for calculating physical observables [76]. This spatial fluence distribution is not considered for simplicity.…”

Section: Resultsmentioning

confidence: 99%

Transient ionization potential depression in nonthermal dense plasmas at high x-ray intensity

et al. 2021

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The advent of x-ray free-electron lasers (XFELs), which provide intense ultrashort x-ray pulses, has brought a new way of creating and analyzing hot and warm dense plasmas in the laboratory. Because of the ultrashort pulse duration, the XFEL-produced plasma will be out of equilibrium at the beginning, and even the electronic subsystem may not reach thermal equilibrium while interacting with a femtosecond timescale pulse. In the dense plasma, the ionization potential depression (IPD) induced by the plasma environment plays a crucial role for understanding and modeling microscopic dynamical processes. However, all theoretical approaches for IPD have been based on local thermal equilibrium (LTE), and it has been controversial to use LTE IPD models for the nonthermal situation. In this work, we propose a non-LTE (NLTE) approach to calculate the IPD effect by combining a quantum-mechanical electronic-structure calculation and a classical molecular dynamics simulation. This hybrid approach enables us to investigate the time evolution of ionization potentials and IPDs during and after the interaction with XFEL pulses, without the limitation of the LTE assumption. In our NLTE approach, the transient IPD values are presented as distributions evolving with time, which cannot be captured by conventional LTE-based models. The time-integrated ionization potential values are in good agreement with benchmark experimental data on solid-density aluminum plasma and other theoretical predictions based on LTE. The present work is promising to provide critical insights into nonequilibrium dynamics of dense plasma formation and thermalization induced by XFEL pulses.

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“…The measured charge-state distribution (CSD), therefore, contains contributions from a range of fluence values. In order to make a quantitative comparison, theoretical CSDs corresponding to each fluence point are convolved with the experimental fluence distribution [51]. This procedure is called volume integration [11,51].…”

Section: Volume-integrated Charge-state Distributions Of Xe At 120mentioning

confidence: 99%

“…In order to make a quantitative comparison, theoretical CSDs corresponding to each fluence point are convolved with the experimental fluence distribution [51]. This procedure is called volume integration [11,51]. Since the pulse-duration dependence of mean charges (also CSDs) is sensitive to fluence values as demonstrated in Fig.…”

Section: Volume-integrated Charge-state Distributions Of Xe At 120mentioning

confidence: 99%

Breakdown of frustrated absorption in x-ray sequential multiphoton ionization

Son

Boll

Santra

2020

Phys. Rev. Research

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We investigate the frustrated absorption phenomenon of atomic systems driven by x-ray pulses of extremely high intensity. When an atom is exposed to intense x-ray pulses generated by x-ray free-electron lasers (XFELs), it undergoes complex ionization dynamics characterized by sequential multiphoton multiple ionization. Counterintuitively, as the pulse duration becomes shorter so that the intensity increases, the ionization becomes suppressed because of hollow-atom formation and the reduction of cross section. This is called frustrated absorption. However, as we report here, the paradigm of frustrated absorption can break down at extremely high intensity. By using a state-of-the-art theoretical tool, we examine the pulse-duration dependence of x-ray multiphoton ionization dynamics of heavy atoms, revealing that the reduced ionization for shorter pulses is due to the suppression of Auger decays, rather than the frustration of photoabsorption. Moreover, we predict a situation where ionization is, in fact, enhanced as the pulse duration is decreased and explain the mechanism why this happens. The present results demonstrate that the breakdown of frustrated absorption will emerge at the highest fluence currently available at XFEL facilities and will play an important role when terawatt-attosecond x-ray pulses come into realization.

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xcalib: a focal spot calibrator for intense X-ray free-electron laser pulses based on the charge state distributions of light atoms

Cited by 18 publications

References 50 publications

Pulse Energy and Pulse Duration Effects in the Ionization and Fragmentation of Iodomethane by Ultraintense Hard X Rays

Pulse Energy and Pulse Duration Effects in the Ionization and Fragmentation of Iodomethane by Ultraintense Hard X Rays

Transient ionization potential depression in nonthermal dense plasmas at high x-ray intensity

Breakdown of frustrated absorption in x-ray sequential multiphoton ionization

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