% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@PHDTHESIS{Aufleger:619959,
      author       = {Aufleger, Lennart},
      othercontributors = {Pfeifer, Thomas and Wolf, Andreas},
      title        = {{N}onlinear spectroscopy on an autoionizing two-electron
                      resonance in intense, extreme ultraviolet fields at a
                      free-electron laser},
      school       = {Heidelberg University},
      type         = {Dissertation},
      publisher    = {Heidelberg University Library},
      reportid     = {PUBDB-2024-08050},
      pages        = {119},
      year         = {2022},
      note         = {Dissertation, Heidelberg University, 2022},
      abstract     = {In this work, the influence of intense extreme-ultraviolet
                      (XUV) fields on helium is experimentally investigated.
                      Therefore, XUV pulses from a free-electron laser (FEL) are
                      combined with transient absorption spectroscopy (TAS) and
                      explored with numerical quantum-mechanical simulations. A
                      novel TAS beamline enables measurements on the prototypical
                      atomic three-body system, helium, at the free-electron laser
                      in Hamburg (FLASH). In particular, the energetically lowest
                      two-electron resonance, 2s2p, with its asymmetric Fano
                      absorption line shape is of interest. This bound state is
                      embedded in the single-ionization continuum and thus
                      represents an atomic interferometer. Its main property, the
                      sensitivity to phase, is used in this work to detect
                      manipulations induced by strong XUV pulses. In the
                      experiments, a distortion of the absorption line is observed
                      in the presence of highly intense XUV pulses. Firstly, the
                      line shape’s symmetry change is investigated with a
                      numerical few-level model simulation and found to be
                      connected to the transient dressing of the excited state.
                      Employing realistically modelled stochastic pulses, the
                      investigation is extended to the line shape’s dependence
                      on the pulse duration. Finally, the line broadening is
                      explained by the model simulation and allows for
                      disentangling the contributing mechanisms, two-photon
                      absorption and the increased reversion to the ground state.},
      cin          = {DOOR ; HAS-User},
      cid          = {I:(DE-H253)HAS-User-20120731},
      pnm          = {6G2 - FLASH (DESY) (POF4-6G2)},
      pid          = {G:(DE-HGF)POF4-6G2},
      experiment   = {EXP:(DE-H253)F-BL2-20150101},
      typ          = {PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:bsz:16-heidok-312094},
      url          = {https://bib-pubdb1.desy.de/record/619959},
}