Molecular Orbital Analysis of High Harmonic Generation

Tunnel ionization of molecules in an intense laser field and subsequent rescattering processes lead to high harmonic generation (HHG). Simultaneous tunneling from multiple orbitals has recently been observed which is not considered in the conventional single-active-electron model. To include such multielectron effects, we have developed a multiconfiguration method that uses time-dependent molecular orbitals. By energy analysis of the orbitals, we found that inner shell and valence shell orbitals interact with each other during the HHG process. The HHG spectra of multiple orbital paths originated from the interactions were calculated.