Investigating Nonsequential Double Ionization Mechanisms With Attosecond Two-Electron Angular Streaking

The emission direction of ionized electrons from atoms and molecules is determined by the strong transient laser field at the moment of ionization. Thus, we can use circularly polarized laser pulses to record the emission direction of two electrons in strong-field double ionization. Mapping the relative emission angle between the two electrons onto their ionization time delay, we show relative emission time delay changes in nonsequential double ionization of a model benzene molecule with a classical ensemble model, within the range from 150 to 400 attoseconds, as the laser intensity decreases. Such emission time delay changes reflect the double ionization mechanism changes from dominant direct impact double ionization to dominant recollision-induced excitation with a subsequent field-ionization mechanism. (C) 2019 Optical Society of America