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@ARTICLE{Kroll:419010,
      author       = {Kroll, Thomas and Weninger, Clemens and Alonso-Mori,
                      Roberto and Sokaras, Dimosthenis and Zhu, Diling and
                      Mercadier, Laurent and Majety, Vinay P. and Marinelli,
                      Agostino and Lutman, Alberto and Guetg, Marc W. and Decker,
                      Franz-Josef and Boutet, Sébastien and Aquila, Andy and
                      Koglin, Jason and Koralek, Jake and DePonte, Daniel P. and
                      Kern, Jan and Fuller, Franklin D. and Pastor, Ernest and
                      Fransson, Thomas and Zhang, Yu and Yano, Junko and
                      Yachandra, Vittal K. and Rohringer, Nina and Bergmann, Uwe},
      title        = {{S}timulated {X}-{R}ay {E}mission {S}pectroscopy in
                      {T}ransition {M}etal {C}omplexes},
      journal      = {Physical review letters},
      volume       = {120},
      number       = {13},
      issn         = {1079-7114},
      address      = {College Park, Md.},
      publisher    = {APS},
      reportid     = {PUBDB-2019-00874},
      pages        = {133203},
      year         = {2018},
      abstract     = {We report the observation and analysis of the gain curve of
                      amplified $Kα$ x-ray emission from solutions of Mn(II) and
                      Mn(VII) complexes using an x-ray free electron laser to
                      create the $1s$ core-hole population inversion. We find
                      spectra at amplification levels extending over 4 orders of
                      magnitude until saturation. We observe bandwidths below the
                      Mn 1s core-hole lifetime broadening in the onset of the
                      stimulated emission. In the exponential amplification regime
                      the resolution corrected spectral width of ∼1.7  eV
                      FWHM is constant over 3 orders of magnitude, pointing to the
                      buildup of transform limited pulses of ∼1  fs
                      duration. Driving the amplification into saturation leads to
                      broadening and a shift of the line. Importantly, the
                      chemical sensitivity of the stimulated x-ray emission to the
                      Mn oxidation state is preserved at power densities of
                      $∼10^{20}$  $W/cm^2$ for the incoming x-ray pulses.
                      Differences in signal sensitivity and spectral information
                      compared to conventional (spontaneous) x-ray emission
                      spectroscopy are discussed. Our findings build a baseline
                      for nonlinear x-ray spectroscopy for a wide range of
                      transition metal complexes in inorganic chemistry,
                      catalysis, and materials science.},
      cin          = {FS-TUX / Eur.XFEL / CFEL-QOX},
      ddc          = {530},
      cid          = {I:(DE-H253)FS-TUX-20170422 / $I:(DE-H253)Eur_XFEL-20120731$
                      / I:(DE-H253)CFEL-QOX-20160915},
      pnm          = {6211 - Extreme States of Matter: From Cold Ions to Hot
                      Plasmas (POF3-621)},
      pid          = {G:(DE-HGF)POF3-6211},
      experiment   = {EXP:(DE-MLZ)NOSPEC-20140101},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:29694162},
      UT           = {WOS:000428394800008},
      doi          = {10.1103/PhysRevLett.120.133203},
      url          = {https://bib-pubdb1.desy.de/record/419010},
}