Correlated Electron Momentum Distribution Research Articles

Double ionization of Ar below the recollision threshold intensity

We use the classical ensemble method to analyze the nonsequential double ionization of Ar atoms at a lower laser intensity. The correlated-electron momentum distribution is shown. The electron trajectories from recollision-induced ionization (RII) and from recollision-induced excitation with subsequent ionization (RESI) are studied separately. We find that the momentum of RESI electrons distributes uniformly in the four quadrants of the momentum distribution diagram, while that of RII electrons distributes mainly in the second and fourth quadrants of the momentum distribution diagram. The Coulomb repulsion between the two electrons is responsible for the anticorrelation emission in RII. The momentum distributions of the fast and the slow electrons observed by Liu et al. [Phys. Rev. Lett. 112, 013003 (2014)] are well reproduced in our simulations.

Evidence of decrease of potential energy in nonsequential double ionization above threshold for electron impact excitation

We study the CEP (carrier envelope phase) dependent correlated electron momentum distributions for nonsequential double ionization of Ar in near-single-cycle short pulses at the intensity of 3.0 × 1014 W/cm2 with a central wavelength of 750 nm measured by Bergues et al [Nat. Comm. 3, 813 (2012)]. A kinematical analysis on the constraints for the correlated electron momenta reveals that the excitation potentials of the parent ion Ar+ are reduced at the instant of scattering.

S-matrix and semiclassical study of electron-electron correlation in strong-field nonsequential double ionization of Ne

The correlated electron momentum distribution for nonsequential double ionization (NSDI) of Ne in a strong linearly polarized laser field is studied by quantum $S$-matrix and semiclassical theories. At low intensity, where the single-return-collision NSDI process dominates, a good agreement between two theories is found. However, at high intensity, two theories are inconsistent with each other, and the semiclassical calculation is qualitatively in agreement with the experimental observation. Our analysis shows that this can be attributed to the neglect of the ion potential in the present $S$-matrix theory, and hence the multiple-return-collision NSDI process, which becomes important at high intensity, is underestimated in the current $S$-matrix theory.

Coulomb-potential effects in nonsequential double ionization under elliptical polarization

Using a semiclassical model, we evaluate the correlated electron momentum distribution from nonsequential double ionization (NSDI) of neon in an elliptically polarized laser field. The momentum distribution pattern exhibits a nontrivial change with the increase of the laser ellipticity, which can be understood as a combined effect of the extra laser electric field and the ionic Coulomb potential on the tunnel-ionized electron trajectory. Especially for large ellipticities ($\ensuremath{\epsilon}>0.2$), multiple return collision trajectory contributes dominantly to the NSDI yield and determines the correlated electron momentum distribution, revealing an indispensable role of ionic Coulomb potential in NSDI dynamics under elliptical polarization. Moreover, the nontrivial evolution of the correlated electron momentum distribution with the ellipticity revealed in our model should be testable by a realistic experiment.

Phase-dependence correlated electron momentum distribution from nonsequential double ionization of N2 by few-cycle laser pulses

Using the classical three-dimensional (3D) ensembles, we have investigated nonsequential double ionization (NSDI) of N2 by phase-stabilized few-cycle pulses. We find that the correlated electron momentum distributions in the direction parallel to the laser field strongly depend on the carrier-envelope phase (CEP) of few-cycle pulses, and this phase dependence is not affected by the alignment of the molecular axis relative to the laser field. Back analysis reveals that the ionization rate of the first electron and the recollision energy play a main role in the electron momentum distributions. Our results suggest that the few-cycle pulses with stabilized phase can serve as a powerful tool to investigate the recollision dynamics in NSDI of molecules.

Controlling nonsequential double ionization via two-color few-cycle pulses

Using the classical three-dimensional ensembles, we have demonstrated the controlling of dynamics in nonsequential double ionization (NSDI) of helium by two-color few-cycle pulses. By changing the relative phase of the two pulses, recollisions leading to NSDI can be restricted in a time interval of several hundreds attosecond nearly before the field extremum and as a result, the correlated electron momentum distribution exhibits a so-far unobserved narrow arc-like structure. This structure reveals a novel energy correlation between the two electrons from NSDI by two-color few-cycle pulses.

Classical Trajectory Diagnosis of a Fingerlike Pattern in the Correlated Electron Momentum Distribution in Strong Field Double Ionization of Helium

With a semiclassical quasistatic model, we identify the distinct roles of nuclear Coulomb attraction, final-state electron repulsion, and the electron-field interaction in forming the fingerlike (or V-shaped) pattern in the correlated electron momentum distribution for helium double ionization in intense laser field [Phys. Rev. Lett. 99, 263002;Phys.Rev.Lett.99, 263003 (2007)]. The underlying microscopic trajectory configurations responsible for asymmetric electron energy sharing after electron-electron collision have been uncovered, and the corresponding subcycle dynamics is analyzed. The correlation pattern is found to be sensitive to the transverse momentum of correlated electrons.

Binary and Recoil Collisions in Strong Field Double Ionization of Helium

We have investigated the correlated momentum distribution of both electrons from nonsequential double ionization of helium in a 800 nm, 4.5 x 10(14 W/cm2 laser field. Using very high resolution coincidence techniques, we find a so-far unobserved fingerlike structure in the correlated electron momentum distribution. The structure can be interpreted as a signature of the microscopic dynamics in the recollision process. We identify features corresponding to the binary and recoil lobe in field-free (e,2e) collisions. This interpretation is supported by analyzing ab initio solutions of a fully correlated three-dimensional helium model.