Phase Measurement of a Fano Resonance Using Tunable Attosecond Pulses

Summary, in English

We study photoionization of argon atoms close to the 3s(2)3p(6) -> 3s(1)3p(6)4p Fano resonance using an attosecond pulse train and a weak infrared probe field. An interferometric technique combined with tunable attosecond pulses allows us to determine the phase of the photoionization amplitude as a function of photon energy. We interpret the experimental results using an analytical two-photon model based on the Fano formalism and obtain quantitative agreement.