The influence of the quantum nature of nuclei in high harmonic generation from H$_2^+$-like molecular ions

We study the full quantum dynamics of a simple molecular ion driven by an intense laser field. In particular we show that the quantum nature of the nuclear dynamics affects the emitted high harmonic generation (HHG) spectra, strongly reshaping the plateau region. In fact, it is evident that the characteristic flat trend is transformed into a descending trend, with the lower harmonics being two orders of magnitude more intense than the higher harmonics. We show that this effect is more pronounced in the lighter isotopic species of H$_2^+$ molecular ions and we also demonstrate that in this case the contribution to HHG from the antibonding electronic energetic surface is of the same order of magnitude as that from the bonding state.