Doubly excited autoionizing states in N-2

Many-body perturbation theory for general model spaces (quasidegenerate theory) has been applied to compute excitation energies for doubly excited autoionizing states in N-2. Special attention is given to the energy range 20-30 eV. A few autoionizing single excited states with excitation energies around 18 eV are also studied. The many-body method is in addition used to compute electric dipole transition moments (oscillator strengths) from the ground state to the doubly excited states. Autoionization rates (lifetimes) are also calculated, as well as partial rates for autoionization to the three lowest electronic states in N-2(+). The computed results show encouraging agreement with resonances observed in branching ratios for vibrationally resolved photoionization cross sections.