Many fundamental processes in matter, like electron-electron or electron-phonon scattering in solids, occur on a time scale ranging from a few tenth of femtoseconds to picoseconds. Experimentally, these ultrafast phenomena are accessed by monitoring the interaction of ultrashort light pulses with a given sample. Among the experimental techniques available nowadays, the so-called pump-probe methods are most frequently used. Despite all the experimental work performed so far, ab-initio theoretical investigations in realistic systems - at least according to our knowledge - are still lacking completely. In the present talk a scheme is given, that describes pump-probe experiments within Kubo's response theory, which in turn can be implemented using the spin-polarized relativistic screened Korringa-Kohn-Rostoker method via a contour integration technique.