Electron Dynamics In Nonsequential Double Ionization Research Articles

Controlling non-sequential double ionization with chirped laser pulse

The non-sequential double ionization (NSDI) of He in a chirped few-cycle laser pulse is studied using a full-dimensional semi-classical model. The NSDI probability is found to be very sensitive to the rate of wavelength change. An abrupt jump is found in the probability distribution during the crossover from up- to down-chirped pulse, followed with a further increase of the probability when keep increasing the rate of wavelength change. In the meantime, the correlated electron momentum distribution transfers from anti-correlated to a correlated pattern. Further analysis reveals the underlying mechanism to be the increase of the kinetic energy of returned electron acquired from the chirped pulse in the re-collision process. The dominant NSDI mechanism transfers from recollision-induced excitation with subsequent field ionization (RESI) to electron-impact ionization (EI). Therefore, the chirped laser pulse could be a useful tool for controlling the electron dynamics in NSDI and beyond.

Universal time delay in the recollision impact ionization pathway of strong-field nonsequential double ionization

With the semiclassical ensemble model, we investigated the correlated electron dynamics in the recollision impact ionization (RII) pathway of strong-field nonsequential double ionization (NSDI) at different laser wavelengths. Our results show that there is a remarkable time delay (about 400 attoseconds) between double ionization and recollision for a considerable part of the RII events. This type of event is responsible for the valley structure in the correlated electron momentum spectra along the laser polarization direction. More interestingly, our results show that this time delay is independent of the wavelength. This universal time delay is of crucial importance for the comprehensive understanding of the correlated electron dynamics in NSDI.

Correlated electron dynamics in nonsequential double ionization by orthogonal two-color laser pulses

We have investigated the correlated electron dynamics in nonsequential double ionization (NSDI) of helium by the orthogonally polarized two-color pulses that consisted of an 800-nm and a 400-nm laser fields using the classical ensemble model. Depending on the relative phase of the two-color field, the electron momentum distributions along the polarization direction of the 800-nm field exhibit a surprisingly strong anticorrelated or correlated behavior. Back analysis reveals that recollisions eventually leading to NSDI are concentrated in a time window as short as several hundreds attoseconds with this scheme. By changing the relative phase of the two-color field, the revisit time of recolliding electron wave packet has been controlled with attosecond precision, which is responsible for the various correlated behaviors of the two electrons. Our results reveal that the orthogonally polarized two-color field can serve as a powerful tool to control the correlated electron dynamics in NSDI.