Role of quantum trajectories associated internuclear-distance on high-order harmonic generation of H2+

We present the role of quantum trajectories on high-order harmonic generation (HHG) related to the various internuclear distances in hydrogen molecule ions in an intense laser field by solving two-dimensional time-dependent Schrödinger equation. We find that the contribution of the long trajectories in HHG is dominant at smaller internuclear distances, but the contribution of the short trajectories is dominant at larger internuclear distances, it implies that the role of quantum trajectories closes to those HHG of the atom. In addition, the HHG spectrum of hydrogen molecule ions exhibits an internuclear distance-dependent double plateau structure which is related to the electron migrating from one nucleus to another one. Combining with the Morlet transform of quantum time-frequency spectrum and an extended semiclassical analysis, the role of quantum trajectories on HHG with the various internuclear distance are clarified.