The Microscopic Dynamics Research Of Atom Double Ionization Forced By Strong Field

In this paper, we investigated the nonsequential double ionization (NSDI) and sequential double ionization (SDI) of atoms (Ar and Xe) by elliptically polarized laser pulses with classical ensemble model. The content mainly contain two parts, one is laser-intensity dependence of NSDI of atoms in elliptically polarized laser pulses and the other is NSDI and SDI of atoms by few-cycle elliptically polarized laser pulses.With a classical ensemble model, we investigated nonsequential double ionization (NSDI) of Argon by elliptically polarized laser pulses. The results show that the correlation behaviors of two electrons depend strongly on the laser intensity. At the relatively high laser intensity, the momentum spectra of two electrons along the long axis of the laser polarization plane are mainly distributed in the first and third quadrants and display V-like structures. However, at the relatively low laser intensity, the momentum spectra of two electrons are mainly distributed in the second and fourth quadrants. By back analyzing the classical trajectories of NSDI, we find that all of the successful NSDI events still come from recollision in the cases of elliptically polarized laser pulses, and the final-state electron repulsion plays a decisive role for the V-like structure along the long axis of the laser polarization plane. In addition, we find that the initial velocity of the first electron at ionization along the short axis of the laser polarization plane are essential for the recollision, and the time delay between the first ionization and recollision depends on the ellipticity strongly.Using a classical ensemble model, we have investigated the correlation behavior of the electrons from NSDI of argon atoms by the elliptically polarized laser pulses. Because of the ellipticity, not only the first returning but also the latter returnings of tunneled electron contribute significantly to NSDI. We have mainly discussed two-kinds events of NSDI originating from the first and the second returnings separately. For the NSDI resulting from the recollision of the first returning, the correlated electron momentum spectrum along the long axis of the laser polarization plane reveals an obvious V-like shape, locating at the first and third quadrants. However, for the NSDI resulting from the recollision of the second returning, the momentum of two electrons is distributed in the four quadrants uniformly. By back analyzing trajectories of these two kinds, we find that recollision energy and the laser phase at recollision are different for the first-and the second-returning trajectories, which are responsible for the difference in the correlated behavior of the final electron momentum.With the classical ensemble model, we have investigated the NSDI of Xe atoms by the elliptically polarized few-cycle laser pulses at the laser intensity2.5×1014W/cm2and the laser wavelength780nm. The results show the momentum spectra of the final-state correlated electron from NSDI along the long axis of the polarization plane are mainly distributed in the first and third quadrants showing strongly correlated behavior at the various carrier-envelop phases (CEPs). The ratio of NSDI yield that distributed in the first and third shows decrease firstly then increase as CEP decreases. By analyzing the trajectories, the events of NSDI still as the result of the recollision at this laser pulse and the processes of NSDI are dominated by (e,2e).In addition, we also found that the laser phase at the recollision strongly depends on CEP.With the classical ensemble model, we have investigated double ionization of xenon atoms by an elliptically polarized few-cycle laser pulse at intensity4×1014W/cm2. The SDI and NSDI exist simultaneously with this laser field. The momentum distributions of SDI and NSDI both strongly depend on CEP. Back analysis shows that the ionization times of both electrons in SDI and the recollision time in NSDI have a strong dependence on CEP, which is responsible for the CEP-dependent momentum distributions of SDI and NSDI. The rich details of SDI and NSDI are intuitively revealed by back analysis of the classical trajectories.