High-order harmonic generation, attosecond pulse train, and non- sequential double ionization in the helium atom under high-intensity femtosecond laser pulses

Abstract

Abstract High-order harmonic generation (HHG), attosecond pulse train (APT), and non-sequential double ionization (NSDI) in the He atom under high intense femtosecond laser pulses are calculated by time-dependent Schrodinger equation (TDSE) in one dimension (1D). By considering the mutual electron-electron and electron-nuclei interactions along with calculating the He atom ground state wave function by imaginary time propagation (ITP) method, besides calculating probability density of electrons, dipole acceleration, HHG, and APT, we could generate the well-known "knee structure" in the probability of the He atom ionization against the intensity in an ionization boundary condition model. The results are in good agreement with the experimental data reported by Walker et al. [B. Walker et al. Phys. Rev. Lett. 73, 1227 (1994)].