Influence Of Vibrational States On High-Order-Harmonic Generation And An Isolated Attosecond Pulse From A N-2 Molecule

The high-order-harmonic generation (HHG) from the N-2 molecule in an intense laser field is investigated by applying the Lewenstein method. The initial state is constructed as a linear combination of the highest occupied molecular orbital (HOMO) and the lower-lying orbital below the HOMO, which is well described by a Gaussian wave packet generated by using the GAMESS-UK package. The HHG with different vibrational states of N-2 are calculated and our results show that the harmonic intensity can be enhanced by higher vibrational states, which can be explained by the ionization probability. We also compared the cases with a different full width at half maximum of laser fields together, which can be well understood by the time-frequency analysis and the three-step model. Finally, the attosecond pulse generation is studied with different vibrational states, where a series of attosecond pulses can be produced with the shortest being 91 as.