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Transient absorption of warm dense matter created by an X-ray free-electron laser

Mercadier, Laurent ; Benediktovitch, Andrei ; Krušič, Špela ; Kas, Joshua J. ; Schlappa, Justine ; Agåker, Marcus LU ; Carley, Robert ; Fazio, Giuseppe ; Gerasimova, Natalia and Kim, Young Yong , et al. (2024) In Nature Physics 20(10). p.1564-1569
Abstract

Warm dense matter is at the boundary between a plasma and a condensed phase and plays a role in astrophysics, planetary science and inertial confinement fusion research. However, its electronic structure and ionic structure upon irradiation with strong laser pulses remain poorly understood. Here, we use an intense and ultrafast X-ray free-electron laser pulse to simultaneously create and characterize warm dense copper using L-edge X-ray absorption spectroscopy over a large irradiation intensity range. Below a pulse intensity of 1015 W cm−2, an absorption peak below the L edge appears, originating from transient depletion of the 3d band. This peak shifts to lower energy with increasing intensity, indicating the... (More)

Warm dense matter is at the boundary between a plasma and a condensed phase and plays a role in astrophysics, planetary science and inertial confinement fusion research. However, its electronic structure and ionic structure upon irradiation with strong laser pulses remain poorly understood. Here, we use an intense and ultrafast X-ray free-electron laser pulse to simultaneously create and characterize warm dense copper using L-edge X-ray absorption spectroscopy over a large irradiation intensity range. Below a pulse intensity of 1015 W cm−2, an absorption peak below the L edge appears, originating from transient depletion of the 3d band. This peak shifts to lower energy with increasing intensity, indicating the movement of the 3d band upon strong X-ray excitation. At higher intensities, substantial ionization and collisions lead to the transition from reverse saturable absorption to saturable absorption of the X-ray free-electron laser pulse, two nonlinear effects that hold promise for X-ray pulse-shaping. We employ theoretical calculations that combine a model based on kinetic Boltzmann equations with finite-temperature real-space density-functional theory to interpret these observations. The results can be used to benchmark non-equilibrium models of electronic structure in warm dense matter.

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publishing date
type
Contribution to journal
publication status
published
subject
in
Nature Physics
volume
20
issue
10
pages
6 pages
publisher
Nature Publishing Group
external identifiers
  • scopus:85199987532
ISSN
1745-2473
DOI
10.1038/s41567-024-02587-w
language
English
LU publication?
yes
id
74b770c0-cc8d-4029-b6d3-cc54abdf20b5
date added to LUP
2024-12-02 09:56:17
date last changed
2025-04-04 15:15:33
@article{74b770c0-cc8d-4029-b6d3-cc54abdf20b5,
  abstract     = {{<p>Warm dense matter is at the boundary between a plasma and a condensed phase and plays a role in astrophysics, planetary science and inertial confinement fusion research. However, its electronic structure and ionic structure upon irradiation with strong laser pulses remain poorly understood. Here, we use an intense and ultrafast X-ray free-electron laser pulse to simultaneously create and characterize warm dense copper using L-edge X-ray absorption spectroscopy over a large irradiation intensity range. Below a pulse intensity of 10<sup>15</sup> W cm<sup>−2</sup>, an absorption peak below the L edge appears, originating from transient depletion of the 3d band. This peak shifts to lower energy with increasing intensity, indicating the movement of the 3d band upon strong X-ray excitation. At higher intensities, substantial ionization and collisions lead to the transition from reverse saturable absorption to saturable absorption of the X-ray free-electron laser pulse, two nonlinear effects that hold promise for X-ray pulse-shaping. We employ theoretical calculations that combine a model based on kinetic Boltzmann equations with finite-temperature real-space density-functional theory to interpret these observations. The results can be used to benchmark non-equilibrium models of electronic structure in warm dense matter.</p>}},
  author       = {{Mercadier, Laurent and Benediktovitch, Andrei and Krušič, Špela and Kas, Joshua J. and Schlappa, Justine and Agåker, Marcus and Carley, Robert and Fazio, Giuseppe and Gerasimova, Natalia and Kim, Young Yong and Le Guyader, Loïc and Mercurio, Giuseppe and Parchenko, Sergii and Rehr, John J. and Rubensson, Jan Erik and Serkez, Svitozar and Stransky, Michal and Teichmann, Martin and Yin, Zhong and Žitnik, Matjaž and Scherz, Andreas and Ziaja, Beata and Rohringer, Nina}},
  issn         = {{1745-2473}},
  language     = {{eng}},
  number       = {{10}},
  pages        = {{1564--1569}},
  publisher    = {{Nature Publishing Group}},
  series       = {{Nature Physics}},
  title        = {{Transient absorption of warm dense matter created by an X-ray free-electron laser}},
  url          = {{http://dx.doi.org/10.1038/s41567-024-02587-w}},
  doi          = {{10.1038/s41567-024-02587-w}},
  volume       = {{20}},
  year         = {{2024}},
}