Charge asymmetric breakup of diatomic molecular ions in an intense ultrashort laser field

Charge asymmetric dissociation of small molecules such as (N$_{2}^{2+})$*$\to $N$^{2+}$+N is a topic of considerable interest. There has been some debate on the mechanisms responsible for the sharing of charge in an intense laser field [1]. We present here a study of the ionization of N$_{2}^{+}$ and CO$^{+}$ molecular ion beams using ultrashort (10-45 fs) 790 nm laser pulses with intensities up to 5$\times $10$^{15}$ W/cm$^{2}$. Employing a coincidence 3D momentum imaging method, we isolate the asymmetric breakup channels (e.g. N$^{2+}$+N) from charge symmetric (e.g. N$^{+}$+N$^{+})$ channels through detection of neutral fragments in coincidence with the ion fragments. Analysis of the kinetic energy release and angular distributions reveal detailed information on the breakup mechanisms. [1] C. Guo, M. Li, and G.N. Gibson, Phys. Rev. Lett. \textbf{82}, 2492, (1999).