Wigner analysis of electron correlation in high-order above-threshold ionization

Abstract

We theoretically investigate the electron correlation effect on high-order above-threshold ionization (HATI) of the helium atom, by numerically solving the time-dependent Schr\"odinger equation. Our simulations show that, due to the electron correlation effect, the HATI amplitude shows a significant enhancement, and moreover, such an enhancement becomes weak for the long laser wavelength or high laser intensity. In terms of a Wigner analysis, we reveal that the HATI enhancement is caused by the Coulomb exclusion between the two electrons during the rescattering. With the increase of laser wavelength or intensity, the return energy of the rescattered electron increases, and accordingly, the Coulomb exclusion effect decreases relatively, leading to that the HATI enhancement becomes weak. Our work provides a deep insight into the two-electron correlated dynamics during the strong-field ionization.