ODD-EVEN HIGH-ORDER HARMONIC GENERATION FROM HELIUM ATOM APPROACHING FROM TIME-DEPENDENT DENSITY FUNCTIONAL THEORY

Tóm tắt

Recently, we found that the even-to-odd ratio of high-order harmonic generation (HHG) emitted from atoms or symmetric molecules in the combination of a mid-IR laser pulse and THz electric field is a universal quantity, i.e., independent of mid-IR laser’s parameters and the choice of the target. However, the targets are considered within the one-electron model, and the conclusions are derived from directly numerically solving the time-dependent Schrӧdinger equation. In this work, we investigate the validation of the even-to-odd universality helium atom consisting of two electrons, applying the time-dependent density functional theory. The results demonstrate that the multi-electron effect manifesting through the repulsive Coulomb and exchange-correlation interactions does not considerably change the universality of the even-to-odd ratio of the helium atom.