The effect on the harmonic intensity from vibrating H2+ driven by the pump-probe laser field has been theoretically investigated. The results show that for the low vibrational state (i.e. v = 0) case, the intensity of the harmonic spectrum is decreased as the delay time of the pump-probe pulse increases. With the increase of the vibrational state (i.e. v = 2), the harmonic intensity differences under different delay times are decreased. When the vibrational state is further increased (i.e. v = 4), the intensity of the harmonic spectrum under the larger delay time is higher than that of the smaller delay time case. Finally, by investigating the time-frequency analysis chart of harmonic spectrum, we reveal the physical mechanism of the harmonic intensity changes.
