Coulomb explosion imaging of fragmentation channels following laser-induced double ionization of N2

Laser-induced double ionization of the N2 molecule leads to non-Coulombic N+ + N+ and N2+ + N fragmentation channels, with well-defined kinetic energy release spectra. The associated fragmentation temporal dynamics is probed using a femtosecond pump-probe scheme based on Coulomb explosion of the dissociating system. The probe laser pulse produces the double ionization of the dissociating N2+2 ion, and the detected probe signal is the energy spectrum of the resulting N2+ + N2+ dissociation channel. The probe excitation takes place at internuclear distances larger than 5 A, where the N2+ + N2+ dissociation imaging channel energy is Coulombic. This excitation scheme allows us to reproduce the N2+2 fragmentation temporal dynamics using a simple model which takes into account the long-range potentials of the N+ + N+ and N2+ + N pathways and the short-range dissociation times. (letter to the editor)