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.

A semiclassical quasistatic model is used to investigate the recollision dynamics in circularly polarized laser fields. A velocity window for recollision to occur is found. Only when the return electron's orbits are irregular does significant double ionization take place. The model reproduces the experimental results for magnesium and explains the apparently conflicting experimental results in terms of an analytical formula that demarcates the phase diagram for the nonsequential double ionization in circularly polarized laser fields.

We investigate the strong-field double ionization using a semiclassical model, in which the recollision-induced excitation-tunneling (RIET) effect has been taken into account with the Wentzel-Kramers-Brillouin (WKB) approach. When the laser intensity is below the recollision threshold, we find that both RIET and multiple recollisions become significant and can produce the anticorrelated (back-to-back) electron pair. Distinct footprints left by these two mechanisms on the correlated momentum spectra have been identified. As another signature of the transition to below the recollision threshold regime, we find that the V-shaped (or fingerlike) structure in the correlated momentum spectra fades away. Our model calculations have been compared with a recent experiment on argon atoms.