By Cnr Ifn
High Harmonic Spectroscopy (HHS) allows studying fundamental processes occurring on time scales from tens of femtoseconds to hundreds of attoseconds by exploiting the intrinsically ultrafast electronic nature of the HHG process. HHG originates from the quiver motion of electrons in matter driven by an ultrashort external laser field. The electron oscillations are associated with a time-dependent emission of coherent EUV and Soft-X photons. In particular, each photon energy of the harmonic spectrum can be associated with a precise clocking in the time frame of the external laser field. For this reason, HHG provides a self-probing time-resolved spectroscopy technique for the generation medium. Additionally, the harmonics spectrum encodes spatial information on the system’s electronic structure. In our laboratories, we apply HHS for exploring complex electronic and molecular dynamics excited by strong-laser fields, including electron-hole dynamics, collective electron dynamics, charge dynamics upon molecular vibrations, and atomic rearrangements in the formation or breaking of chemical bonds.
