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

Abstract

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.