S-matrix and semiclassical study of electron-electron correlation in strong-field nonsequential double ionization of Ne

Abstract

The correlated electron momentum distribution for nonsequential double ionization (NSDI) of Ne in a strong linearly polarized laser field is studied by quantum $S$-matrix and semiclassical theories. At low intensity, where the single-return-collision NSDI process dominates, a good agreement between two theories is found. However, at high intensity, two theories are inconsistent with each other, and the semiclassical calculation is qualitatively in agreement with the experimental observation. Our analysis shows that this can be attributed to the neglect of the ion potential in the present $S$-matrix theory, and hence the multiple-return-collision NSDI process, which becomes important at high intensity, is underestimated in the current $S$-matrix theory.