Temporal Behaviour of Harmonics from One-Dimensional H⁺₂ in an Ultrashort Laser Pulse

With the method of wavelet transform, we consider the temporal
behaviour of high-order harmonic generation from one-dimensional H⁺₂ exposed to an ultrashort laser pulse with a duration of tens of femtoseconds. The results, which are calculated by numerically solving the corresponding time-dependent Schrödinger equation with the split-operator method in the non-Born-Oppenheimer approach, show that: (1) The high-order harmonics in the cut-off range emitted as a train of pulses have better coherence than those in the plateau. (2) The harmonics are emitted early in time when the intensity of laser pulse increases.