High-order harmonic generation in vibrating two-electron molecules

By solving the time-dependent Schrödinger equation numerically, we simulate high-order harmonic generation from one-dimensional hydrogen molecules driven by intense laser pulses of different wavelengths. The electron-electron interaction and the vibrational degree of freedom are treated fully quantum mechanically. We show that the ratio of harmonic signals from D2 and H2 can be understood as a consequence of two-center interference in the presence of nuclear motion. For 800 nm laser wavelength, high-order harmonic generation is essentially a one-electron process. For 1500 nm the interaction of both electrons with the laser field should be taken into account in the numerical calculation. Nevertheless, a simple model based on the shortest possible trajectories of a single active electron in the laser field predicts the ratio D2/H2 reasonably well.