  In attosecond streaking, an electron is released by a short xuv pulse into a
strong near infrared laser field. When the laser coupling between two states in
the target is weak relative to the detuning, the streaking technique, which
allows for a complete determination of the driving field, also gives an
accurate measurement of the relative phase of the atomic or molecular
ionization matrix elements from the two states through the interference from
the two channels. The interference may change the phase of the photoelectron
streaking signal within the envelope of the ir field, an effect to be accounted
for when reconstructing short pulses from the photoelectron signal and in
attosecond time-resolved measurements.
