Femtosecond pulses as probe of the atomic structure under strong irradiation

Summary, in English

Huge dynamic Stark shifts of atomic energy levels in xenon induced by high-intensity laser light have been measured by a new method based upon multiphoton ionization by a tunable femtosecond laser source. Stark-induced multiphoton resonances appear as identifiable structures in the photoelectron energy spectra. The change in the structures positions, when the photon energy is tuned, is directly related to the energy change of the atomic levels as a function of intensity. Shifts of the order of the electron-volt have thus been measured in xenon and found to vary linearly-with intensity.