Multiphoton Ionization from Multiple Orbitals of N2 in Strong Laser Fields

We investigate multiphoton ionization （MPI） of N2 exposed to femtosecond laser fields at 400nm and 80Onto experimentally. Photoelectron energy spectra are measured with a high resolution photoelectron spectrometer at laser intensities up to 10^14 W/cm^2. Prominent resonant peaks observed at 400nm can be attributed to the resonance with molecular Rydberg states corresponding to different molecular orbitals, revealing the importance of the multiple orbitals contribution in strong field molecular dynamics.