Classical Simulations Including Electron Correlations for Sequential Double Ionization

Abstract

With a classical ensemble model that including electron correlations during the whole ionization process, we investigated strong-field sequential double ionization of Ar by elliptically polarized pulses at the quantitative level. The experimentally observed intensity-dependent three-band or four-band structures in the ion momentum distributions are well reproduced with this classical model. More importantly, the experimentally measured ionization time of the second electrons [A. N. Pfeiffer et al., Nature Phys. 7, 428 (2011)], which can not be predicted by the standard independent-electron model, is quantitatively reproduced by this fully classical correlated model. The success of our work encourages classical description and interpretation of the complex multi-electron effects in strong field ionization where nonperturbative quantum approaches are currently not feasible.PACS numbers: 32.80. Rm, 31.90.+s, 32.80.Fb Among various intense laser-induced phenomena, strong field double ionization (DI) is one of the most important and fundamental processes. During the past decades, a great number of experimental as well as theoretical studies have been performed on this area. It has been known that DI proceeds either sequentially or nonsequentially. In nonsequential double ionization (NSDI), the second electron is ionized by the recollision of the first tunneled electron [1]. Because of this recollision, the two electrons from NSDI exhibit a highly correlated behavior [2][3][4][5][6]. In sequential double ionization (SDI), it is usually assumed that no correlation exists between the two electrons, and thus the ionization of the electrons can be treated as two independent tunneling-ionization steps. However, this assumption has been called into doubt by recent experiments [7,8]. In Ref. [7], it has been shown that there is a clear angular correlation between the two electrons from SDI, which implies that the successive ionization steps are not independent in SDI. In Ref.[8], the authors found that the ionization time of the second electron from SDI is much earlier than the prediction of the independent-electron model. These observations declare that the electron correlations in SDI should be reexamined carefully.Theoretically, an accurate description of the electron correlations in DI needs full quantum theory. However, due to the enormous computational demand, the solution of the time-dependent schrödinger equation of the two-electron system in the strong field, especially in the case of elliptically polarized laser fields, is not feasible currently. Instead, a fully classical treatment of the twoand multi-electron systems proposed by Eberly et al. has been well established [9][10][11][12]. During the past decade, this model has been successful in exploring the strong-field ionization processes at the qualitative level. However, * Corresponding author: lupeixiang@mail.hust.edu.cn it fails when made a quantitative comparison with experiments. For example, in ref. [13] it has been shown that the saturation intensity ...

Spectrally resolved spatiotemporal features of quantum paths in high-order-harmonic generation

“…These ultrashort pulses can serve as an important tool for detecting the ultrafast electron dynamics inside atoms or molecules [9][10][11] as well as inaugurating a new domain for timeresolved metrology and spectroscopy on attosecond time scale [4,12,13]. Due to these applications, HHG has been a subject of great interest in the past two decades.…”

Complete characterization of single-cycle double ionization of argon from the nonsequential to the sequential ionization regime

“…Strong-field multiple ionization of atoms is widely regarded as a classic example of multielectron dynamics in an external field and has attracted considerable interest of experimentalists [1][2][3][4][5][6] and theorists [7][8][9][10][11] alike. Double ionization in particular is a process characterized by different intensitydependent regimes [12].…”

Switching classical trajectory Monte Carlo method to describe two-active-electron collisions

“…This approach, which employs classical mechanics to describe nonadiabatic dynamics in terms of noninteracting electron trajectories, is referred to as the classical trajectory Monte Carlo (CTMC) method. Beyond atomic collisions, CTMC is also widely used in the framework of laser-matter interactions [7][8][9][10][11][12]. However, the applicability of CTMC is usually restricted to one-active-electron dynamics, since many-electron systems are classically unstable and subject to artificial autoionization (see [13] and references therein).…”