Time-resolved X-ray diffraction with accelerator- and laser-plasma-based X-ray sources

摘要: Femtosecond X-ray pulses are a powerful tool to investigate atomic motions triggered by femtosecond pump pulses. This thesis is dedicated the production of such and their use in optical – probe measurement. This describes laser-plasma-based sources available at University Duisburg-Essen. Part it consists description design, built-up characterization new “modular” source optimize flux onto sample under investigation. The acoustic wave generation optically excited semiconductor (gallium arsenide) metal (gold) was performed using The physical answer material modeled simple strain model for semiconductor, pressure metal, order gain information on interplay electronic thermal pressures rising after excitation. Whereas no reliable could be obtain gallium arsenide (principally due bulk), gold achieved very good agreement, providing useful information. relaxation time electron lattice energy  found (5.0±0.3) ps, ratio Gruneisen parameters e / i = (0.5±0.1). also Sub-Picosecond Pulse Source (SPPS) which existed (formally) Stanford Linear Accelerator Center, an accelerator-based source, two measurements with it. first one detailed investigation phonon softening A1g mode launch bismuth upon fluence Detailed concerning equilibrium position frequency were obtained over extended laser fluences. second measurement concerned study liquid phase dynamics newly formed following ultrafast melting indium antimonide. formation its development excitations close ablation threshold revealed. Such results possible obtain, unprecedented combination short pulse duration brightness SPPS.