TU Berlin

AG KrikunovaAG Krikunova

Inhalt des Dokuments

zur Navigation

AG Krikunova Ultrakurzzeitphysik

Novel light sources such as laser-based high harmonic generation (HHG) or accelerator-based free-electron-laser (FEL) have triggered a wide range of experiments for studies dynamical processes on the femto- and even on the attosecond time scale. In particular, the interaction of ultra-short, high-energy, coherent light pulses with matter represents one of the most exciting topics in atomic and molecular physics. Processes such ionization and dissociation dynamics, charge transfer as well as structural reorganization of complex systems can be followed in real time.  Short wavelengths provide chemical sensitivity by the access to the electron core-levels, and give access to bulk properties due to their long penetration depth. Also high peak intensities of FEL sources have led to the discoveries and characterisation of new states of matter and nonlinear phenomena. 

Time-resolved pump-probe spectroscopy

Experimental setup

We are working on the development and implementation of new spectroscopic techniques to achieve spectral selectivity of distinct relaxation pathways out of a multitude of reaction channels which can simultaneously be excited in the sample by the illumination with FEL or HHG pulses. The approach is based on the so called pump-probe principle, by using pump and probe pulses from different parts of the electromagnetic spectrum e.g. soft-X-ray/visible or soft-X-ray/THz pulses.  The advantage of using two color pulse pair relies on the different interactions mechanisms with the sample. While the radiation in the visible range acts on the weakly bound valence and Rydberg electrons (even at high intensities through multi-photon or field ionization processes), the (soft)-X-ray radiation will preferably ionize inner-shell electrons. The THz-radiation, however, acts effectively on the free charge carriers or on the electron wave packet in continuum. Thus, greatly different light frequencies drive different physical mechanisms and allow, therefore, unveiling the action of pump and probing pulses on the target. Under the certain experimental conditions the temporal resolution in such approach can be better than dictated by the convolution of pump and probe pulse profiles.      



Schnellnavigation zur Seite über Nummerneingabe