Electron excitation and `cascadeʹ ionization of diatomic molecules with ultra-short pulses of strong IR lasers

The dynamics of molecular electron excitation and ionization is studied in real time for ultra-short IR laser pulses of intensity I>1013 W/cm2. The multi-electron molecule is modeled by a system of two active electrons moving in the field of the frozen core. The time dependence of electron probability, electron energy, and one-electron/two-electron ionization probability are calculated for the example of the N2 molecule and a laser pulse with λ=800 nm, τ=5 fs. The electron dynamics of the pulse-excited molecule is considered also after the pulse end. The results show that in strong IR pulses of I⩾1016 W/cm2 the molecule undergoes a cascade ionization, where the one electron is emitted with the same probability as a pair of electrons.