Reconstruction of attosecond harmonic beating by interference of two-photon transitions

A method is proposed for detailed determination of the temporal structure of XUV pulses. The method is especially suited for diagnostics on attosecond pulses and pulse trains that originate from temporal beating of various harmonics of an ultrashort laser pulse. A recent experiment already showed the feasibility of this method when applied to long attosecond pulse trains, where it measured the average pulse characteristics. Here we argue that the same method is also suitable for determining differences between the individual attosecond pulses in a short train, or the properties of a single attosecond pulse.