Electron-electron dynamics in laser-induced nonsequential double ionization

Abstract

For the description of nonsequential double ionization (NSDI) of rare-gas atoms by a strong linearly polarized laser field, the quantum-mechanical S-matrix diagram that incorporates rescattering impact ionization is evaluated in the strong-field approximation. We employ a uniform approximation, which is a generalization of the standard saddle-point approximation. We systematically analyze the manifestations of the electron-electron interaction in the momentum distributions of the ejected electrons: for the interaction, by which the returning electron frees the bound electron, we adopt either a (three-body) contact interaction or a Coulomb interaction, and we do or do not incorporate the mutual Coulomb repulsion of the two electrons in their final state. In particular, we investigate the correlation of the momentum components parallel to the laser-field polarization, with the transverse momentum components either restricted to certain finite ranges or entirely summed over. In the latter case, agreement with experimental data is best for the contact interaction and without final-state repulsion. In the former, if the transverse momenta are restricted to small values, comparison of theory with the data shows evidence of Coulomb effects. We propose that experimental data selecting events with small transverse momenta of both electrons are particularly promising in the elucidation of the dynamics of NSDI. Also, a classical approximation of the quantum-mechanical S matrix is formulated and shown to work very well inside the classically allowed region.

Binary and Recoil Collisions in Strong Field Double Ionization of Helium

“…In many experiments [4 -9] a maximum was observed for the emission of both electrons in the same direction with similar momentum components parallel to the laser field (k k a k k b ). This seemingly well established maximum is supported by numerous theoretical results (e.g., [10 -12]) but is in conflict with others [13][14][15][16][17] which predict a minimum.…”

Laser-induced nonsequential double ionization at and above the recollision-excitation-tunneling threshold

“…Electron-impact ionization is possibly the most extensively investigated NSDI mechanism [5][6][7][8][9][10][11][12][13]. This is due to the fact that, until the past few years, it was sufficient to describe key features observed experimentally in the electron momentum distributions.…”

Exchange and polarization effect in high-order harmonic imaging of molecular structures

“…An alternative language developed by Kuchiev and Ostrovsky [41,46,47], which describes HHG in terms of multiple channels, leads to the same physical picture once the saddle point method is applied [41]. The language of quantum trajectories has been used extensively and successfully for analyzing various aspects of strong-field dynamics, including the properties of harmonic generation and other recollision-driven physical processes (see, e.g., [48][49][50][51][52][53][54][55][56][57][58][59][60]). Particularly important in harmonic generation are the so-called "short" trajectories, which correspond to the simplest electron motion in the continuum with the shortest time delay between ionization and recombination.…”