Strong-field double ionization in a three-electron atom: Momentum-distribution analysis

We study strong-field double ionization in a three-electron atom by applying a simplified, reduced-dimensionality model with three active electrons. The influence of the spin-induced symmetry of the spatial part of the wave function on the final two-photoelectron momentum distribution is discussed. We identify partial momentum distributions originating from different sets of spins of outgoing electrons providing in this way a quantum support connection between the V-structure and direct ionization typically explained classically. Changes in the momentum distribution with increasing field amplitude obtained in our simplified model are shown to be well correlated with the experimental data known from the literature. The possible relation between the observed dependencies and different ionization mechanisms is discussed.