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@ARTICLE{Mercadier:517332,
      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},
      title        = {{T}ransient absorption of warm dense matter created by an
                      {X}-ray free-electron laser},
      journal      = {Nature physics},
      volume       = {20},
      number       = {10},
      issn         = {1745-2473},
      address      = {Basingstoke},
      publisher    = {Nature Publishing Group},
      reportid     = {PUBDB-2023-00385},
      pages        = {1564-1569},
      year         = {2024},
      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 10$^{15}$ 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.},
      cin          = {FS-CFEL-XM / $XFEL_E2_SCS$ / FS-TUX},
      ddc          = {530},
      cid          = {I:(DE-H253)FS-CFEL-XM-20210408 /
                      $I:(DE-H253)XFEL_E2_SCS-20210408$ /
                      I:(DE-H253)FS-TUX-20170422},
      pnm          = {631 - Matter – Dynamics, Mechanisms and Control
                      (POF4-631) / DFG project G:(GEPRIS)390715994 - EXC 2056:
                      CUI: Advanced Imaging of Matter (390715994) / DFG project
                      G:(GEPRIS)194651731 - EXC 1074: Hamburger Zentrum für
                      ultraschnelle Beobachtung (CUI): Struktur, Dynamik und
                      Kontrolle von Materie auf atomarer Skala (194651731)},
      pid          = {G:(DE-HGF)POF4-631 / G:(GEPRIS)390715994 /
                      G:(GEPRIS)194651731},
      experiment   = {EXP:(DE-MLZ)NOSPEC-20140101},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:001279238900009},
      doi          = {10.1038/s41567-024-02587-w},
      url          = {https://bib-pubdb1.desy.de/record/517332},
}