Abstract
We describe a method for the complete temporal characterization of attosecond extreme ultraviolet (xuv) fields. An electron wave packet is generated in the continuum by photoionizing atoms with the attosecond field, and a low-frequency dressing laser pulse is used as a phase gate for frequency-resolved-optical-gating-like measurements on this wave packet. This method is valid for xuv fields of an arbitrary temporal structure, e.g., trains of nonidentical attosecond pulses. It establishes a direct connection between the main attosecond characterization techniques demonstrated experimentally so far, and considerably extends their scope, thus providing a general perspective on attosecond metrology.