Comprehensive analysis of strong-field ionization and dissociation of diatomic nitrogen

Accurate potential-energy curves are used consistently instead of Coulombic curves to determine the internuclear separation at ionization, Rᵢₒₙ, in a strong laser field, for charge states of N₂ up to N₂⁵⁺. Furthermore, we exlude the kinetic energy gained from previous ionization steps in determining Rᵢₒₙ. With these improvements, we analyze various dissociation pathways from N₂²⁺ to N₂⁵⁺ and find that the charge symmetric pathways do not give physical results. In fact, it appears that all ionization up to N₂⁵⁺ involves the charge asymmetric channel N₂⁴⁺→N⁺+N³⁺. By determining the time between each ionization step, we observe the competition between laser intensity and internuclear separation in determining the molecular ionization rate. Finally, our data are consistent with recent observations that short pulse (130 fs) ionization leaves fragments in electronically excited states whereas long pulse (>600 fs) ionization leaves them in ground electronic states.