Fully differential double photoionization of Li₂ molecule

The angular- and energy-differential cross sections for single photon double ionization of diatomic Li₂ are reported in the molecular frame; this represents a fully differential theoretical study of double ionization from a molecule with more than two electrons. In addition to being a many-electron molecular target possessing core electrons whose interactions influence the outgoing valence electrons, the symmetry of the overall initial and final states are analogous with the same process in H₂, thus permitting a direct comparison of the body-frame angular distributions that result from double ionization from these two molecular targets. We also examine the nature of initial state correlation in a natural orbital expansion for which we also compare with H. The advance of ab initio methods described here to molecules with more than two electrons represents an important and necessary step towards being able to describe even the simplest many-electron molecular double photoionization event.