Control of molecular excitation during the plasma generation of a femtosecond laser pulse

From a classical dynamic simulation, we find the kinetic energy of the electrons generated during laser plasma generation depends on the laser polarization and intensity. The electron kinetic energy reaches its maximum with a fixed laser intensity for circularly polarized laser pulse. The fluorescence spectra at 380.4 nm from N-2 and 391.3 nm from N-2(+) are measured; these are generated by both the direct excitation and electron collision excitation. The electron collision excitation is determined by the electron energy and reaches the maximal with a circularly polarized pulse.