Multiphoton Ionization of Helium with Extreme Ultraviolet Light at the 
Free-Electron Laser in Hamburg

Straub, Michael

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学位論文

Multiphoton Ionization of Helium with Extreme Ultraviolet Light at the Free-Electron Laser in Hamburg

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Straub, Michael
Division Prof. Dr. Thomas Pfeifer, MPI for Nuclear Physics, Max Planck Society;

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Master_thesis_MichaelStraub.pdf
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引用

Straub, M. (2022). Multiphoton Ionization of Helium with Extreme Ultraviolet Light at the Free-Electron Laser in Hamburg. Master Thesis, Ruprecht-Karls-Universität, Heidelberg.

引用: https://hdl.handle.net/21.11116/0000-000A-1646-F

要旨

In this thesis, multi-photon ionization of helium is studied using extreme ultraviolet
(XUV) light from the Free Electron Laser in Hamburg (FLASH). The
highly correlated electron dynamics is measured indirectly by recoil-ion momentum
spectroscopy using a reaction microscope. In addition, a new XUV photon
spectrometer is used to measure the incoming FEL spectra on a shot-to-shot
basis at 100 kHz repetition rate. With a resolution well below 100meV, the intrinsic
pulse structure of the FEL can be resolved. Numerical results validate
a novel technique that combines recoil-ion and photon spectroscopy to measure
two-photon resonances at resolutions below the FEL-bandwidth. First experimental
results probing a two-photon Fano-resonance in helium at 30 eV photon
energy are presented.
In addition, two-photon double ionization is measured in the sequential and
direct regime at photon energies between 40 eV and 57 eV. We are able to observe
the emergence of the virtual sequential process and compare the results with
calculations solving the Schrödinger equation.