Attosecond-resolved electron emission in nonsequential double ionization

We have investigated the correlated electron dynamics in nonsequential double ionization (NSDI) of xenon by the orthogonally polarized two-color pulses consisting of 800- and 1600-nm laser fields. The two-electron momentum distributions are sensitively dependent on the relative phase of the two pulses. By tracing the history of double ionization trajectories, we find that the revisit time of the returning electron wave packet is controlled with attosecond accuracy. After recollision, one electron is ionized immediately while the other electron is either released immediately or excited with subsequent field ionization. The release time of the excited electron is also steered with attosecond resolution by changing the relative phase of the orthogonal two-color pulses. The attosecond-resolved control of the revisit time of the returning electron wave packet and the release time of the excited electron is responsible for the phase dependence of the correlated behaviors of the two electrons. These results indicate that we can trace the emission of the two electrons in NSDI on attosecond time scales.