Dependence of harmonic intensity on internuclear distance from stretched H2+ driven by a linearly polarized laser field

We theoretically investigate the high-order harmonic spectra from stretched H2+ in a linearly polarized laser pulse by numerically solving the two-dimensional time-dependent Schrödinger equation (2D-TDSE). The numerical results show that the harmonic intensity decreases with the increase of the internuclear distance R in the low-order region of the below-threshold harmonic (BTH) for R=6, 8, 10, and the harmonic intensity is enhanced with the increase of the internuclear distance R in the plateau region of the high-order harmonic spectra for R=5, 7, 9, which is illustrated by the populations of the ground state and the first excited state of H2+, the wavelet time-frequency analysis and the ionization probability. In addition, we investigate the dependence of the harmonic intensity on the wavelength and the peak intensity of the driving laser field.