Laser-induced nonsequential double ionization in diatomic molecules: one and two-center rescattering scenarios

TL;DR

This paper explores laser-induced nonsequential double ionization in diatomic molecules, analyzing how different rescattering scenarios and gauge choices affect electron momentum distributions and quantum interference patterns.

Contribution

It introduces modified saddle-point equations to distinguish contributions of various scattering scenarios and compares length and velocity gauge formulations in the context of molecular ionization.

Findings

Quantum interference affects maxima and minima in electron momentum distributions.

Gauge choice influences asymmetry and potential-energy shifts in the distributions.

Interference patterns depend on the topological similarity of scattering scenarios.

Abstract

We investigate laser-induced nonsequential double ionization from aligned diatomic molecules, using the strong-field approximation in its length and velocity gauge formulations. Throughout, we consider that the first electron dislodges the second by electron-impact ionization. Employing modified saddle-point equations, we single out the contributions of different scattering scenarios to the maxima and minima observed in the differential electron momentum distributions. We show that the quantum interference between the electron orbits starting and ending at a specific center $C_{j}$%, and those starting at $C_{j}$ and ending at a different center $C_{\nu}$ leads to the same maxima as minima as if all possible scenarios are taken. There exist, however, quantitative differences as far as the gauge choice is concerned. Indeed, while the velocity-gauge distributions obtained employing only the above-mentioned processes are practically identical to the overall distributions, their length-gauge counterparts exhibit an asymmetry in the positive and negative momentum regions. This asymmetry is due to additional potential-energy shifts which are only present in the length-gauge formulation, and which, depending on the center, sink or increase the potential barrier through which the first electron tunnels. In contrast, the interference between topologically similar scenarios leads at most to patterns whose positions, in momentum space, do not agree with the overall interference condition, neither in the length nor in the velocity gauge.