Interference effects in high-order harmonic generation with molecules

We study high-order harmonic generation for ${\mathrm{H}}_2^{+}$ and ${\mathrm{H}}_2$ model molecules in linearly polarized laser pulses by numerical solution of the Schrödinger equation. Maxima and minima due to intramolecular interference are found in the dependence of the harmonic intensities on the internuclear distance and on the orientation of the molecules. These extrema can be approximately predicted by regarding them as the result of interference between two radiating point sources located at the positions of the nuclei.