Effect of nuclear motion observed in high-order harmonic generation from D2/H2 molecules with intense multi-cycle 1300 nm and 800 nm pulses

We investigate high-order harmonic generation from D2/H2 molecules with intense multi-cycle pulses centred both at 1300 nm (60 fs) and at 800 nm (50 fs) together with that from N2/Ar as a reference. The experimental observations with 1300 nm pulses are different from those with 800 nm pulses both in spectral shapes and in intensity ratios . The effect of nuclear motion in D2 and H2 is more distinctive for 1300 nm pulses than for 800 nm pulses. With multi-cycle pulses of 50?60 fs, the intensity ratios are found to be higher for both 800 nm and 1300 nm pulses than those with few-cycle pulses of 8 fs, which is attributed partly to the contribution of the coupling between the 1s?g and 2p?u states in D+2 and H+2 molecular ions during the higher order returns of the electron wave packets.