The target of this laboratory is the generation and application of high-energy attosecond pulses, produced by high-order order harmonic generation (HHG) in noble gases. The temporal resolution provided by the attosecond pulses allows one to follow the electron dynamics in atoms, molecules and nanostructures. Particularly interesting is the investigation of the charge migration process in biomolecules, which is at the basis of the transmission of biological signals in proteins and DNA.
The driving source is a Ti:sapphire amplified laser system which generates 25 fs pulses with an energy of 6 mJ, repetition rate of 1 kHz and stabilized carrier envelope phase (FEMTOLASERS – Femtopower Pro V CEP). These pulses are compressed by using the hollow fiber technique in combination with ultrabroad band chirped mirrors down to 4 fs withan energy of 2.5 mJ. Due to the high energy of the laser pulses the pressure gradient scheme has been implemented in the hollow fiber setup.
Extreme ultraviolet (XUV) attosecond pulses are produced by focusing the high-energy few-optical cycle pulses in a gas cell filled with noble gases. The generated XUV radiation is focused by a toroidal mirror in the interaction chamber where the sample under investigation is placed. The attosecond beamline allows one to perform pump-probe measurements with attosecond temporal resolution and to fully characterize the XUV pulses. The spectral characteristics of the XUV radiation are measured by using a flat-field grazing incidence spectrometer. A velocity map imaging spectrometer (VMI) is used in the attosecond beamline to measure the momenta of electrons and ions generated by the attosecond pulses focused on the sample in gas phase.