TY  - GEN
UR  - https://archiv.ub.uni-heidelberg.de/volltextserver/24786/
Y1  - 2018///
A1  - Schmid, Georg
TI  - Two-Color Pump-Probe Experiments on Small Quantum Systems at the Free-Electron Laser in Hamburg
AV  - public
ID  - heidok24786
N2  - Within this thesis, the dynamical response of small quantum systems after the absorption of multiple extreme-ultraviolet (XUV) photons is studied via two-color pump-probe experiments at the free-electron laser (FEL) in Hamburg
(FLASH) by employing many-particle recoil-ion momentum spectroscopy.
The multi-photon ionization of argon atoms is investigated at a photon energy of 27 eV and FEL intensities of 10^13 - 10^14 W/cm^2. The sequential ionization channel is found to dominate and intermediate resonances are revealed by a delayed infrared (IR) laser pulse.
Molecular hydrogen (H2) is studied at a photon energy of 28.2 eV. Dissociation via excited states and fragmentation by sequential two-photon ionization are observed. In addition, it is shown how the ground-state dissociation of H2+ can be used as a tool to determine the temporal overlap between an XUV and IR laser pulse.
In the argon dimer, multiple interatomic relaxation processes are triggered by the absorption of several 27-eV-photons. Besides interatomic Coulombic decay (ICD), frustrated triple ionization and charge transfer at crossings of potential energy curves are observed. The lifetime of charge transfer is determined to be (531 +- 136) fs using an XUV-IR pump-probe scheme.
The employed reaction microscope is upgraded by an in-line XUV split-delay and focussing optics, which was designed and commissioned as part of this thesis.
ER  -