Methods for measuring single attosecond x-ray pulses

When an atom is ionized by an x-ray pulse in the presence of a laser field, the drift velocity of photoelectrons shows the phase dependence on the dressing field. We show how to use this effect to characterize single attosecond x-ray pulses. (i) Attosecond streak camera-the distortion of the photoelectron spectra induced by the laser field is used to map the temporal shape of the x-ray pulse to the photoelectron spectra. (ii) Attosecond SPIDER (spectral phase interferometry for direct electric-field reconstruction)-the spectral shearing interferometry of photoelectrons is used to directly retrieve the spectral phase of the x-ray pulse from the photoelectron spectra.