Theoretical study of the femtosecond-resolved photoelectron spectrum of the N2 molecule

The effect of laser fields on the N2 interaction potentials is obtained by simulating the time-resolved photoelectron spectrum (TRPES) with time-dependent wavepacket method. The calculated results show that at low intensities the valence states can be seen, while at high intensities the vibration structure of the molecular Rydberg states cancels out in the photoelectron spectrum leading to sharp atomic-like series. Two conclusions can be derived from the calculation: first, the B state is the final state for 308-nm ionization with intensities higher than 2.4 × 1014 W/cm2, and second, the ionic populations of N2+ present the same dependence on laser intensities.