| Free Electron Laser as FLASH provide very short pulses of VUV and soft X-ray radiation with extremely high brilliance. These properties make it possible to study multi-photon ionization processes of free atoms and molecules by angle resolved photoelectron spectroscopy. First show case examples regarding the intensity dependence and angular distributions of photoelectrons emitted by theses processes will be presented and compared with the results of related experiments. FEL-based experiments exploiting the potentially fs- time structure of these light sources are still in their infancy. Hence, complementary approaches such as the core-hole clock based Doppler electron-spectroscopy provided first results on the tunnelling time of core-electrons in diatomic homonuclear molecules. The corresponding results obtained from the asymmetric angular distributions of the electrons emitted from core-excited O2 during dissociation will be presented and discussed in the context of future real time experiments at FLASH. |
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