6p1/2,3/2nf J = 1-5 autoionizing series of Barium

The 6pnf series of barium converging to both 6p1/2 and 6p3/2 limits were investigated in a two-step pulsed-laser experiment. From 6s5d 3D1,2,3 metastable atoms, discharge populated in an atomic beam, 11 out of the full manifold of 12 autoionizing 6p1/2,3/2nf J=15 Rydberg series were excited via selected 5d6p J=04 doubly excited intermediate states. For each value of the total angular momentum J, the data were analyzed using R-shifted multichannel-quantum-defect theory. The autoionization rates of the different series compare well with a model for autoionization based upon only a direct Coulomb interaction mechanism with neglect of exchange effects. The multiplet level structure of the 6pnf configuration for a particular n Rydberg manifold was analyzed in terms of Slater integrals. The level ordering of 6pnf J substates could only be explained by including a large exchange parameter. Some 6pnp series were also observed, in particular 6p3/2np3/2 J=3. © 1991 The American Physical Society