The nonsequential double ionization of Ar atoms with different initial angular momenta irradiated by a circularly polarized laser pulse

Abstract

The non-sequential double ionization process of Ar atoms with different initial angular momenta in the 500 nm circularly polarized field is investigated with a classical ensemble model. The numerical results show that, under the circularly polarized laser pulse, the double ionization yield as a function of the laser intensity for Ar atoms with different initial angular momenta exhibit an obvious Knee structure. The ionization yield in the counter-rotating case where the electronic initial rotation direction is opposite to the vector potential of the laser field, significantly higher than that in the co-rotating case where the electronic initial rotation direction is consistent with the vector potential of the laser field. Based on the classical trajectory analysis, it is found that this ionization difference comes from the angle between the direction of the electronic momentum and the force of the laser field at the single ionization instant. The angle in the counter-rotating case is greater than that in the co-rotating case, and the counter-rotating electrons are more likely to return to the parent ion for recollision. Besides, the recollision intants of Ar atoms with the different initial angular momenta are mapped to the electron momentum spectrum. This may provide a method to obtain the electron’s recollision instant of Ar atoms with different initial angular momenta.