Effects of Bounding Potential on High-Order Harmonic Generation with H₂⁺

We present harmonic spectra from hydrogen molecular ions with different ionization energy I_p. By comparing the recombination matrix element from helium ions and hydrogen molecular ions, we verify that the interference effect in high-order harmonic generation originates from the recombination interference. A numerical study on recombination matrix elements in 1D shows that ω=E_k+I_p holds only when an exact continuum wavefunction is used, and the positions of extrema in harmonic spectra can be predicted accurately. We demonstrate that the positions of extrema in harmonic spectra are mainly affected by bounding potential dependence of the recombination interference.