The critical double-well in Ba+: many-body approach by the g-Hartree method

A novel many-body approach, developed recently for atoms (the g-Hartree method), has been applied to the critical double-well problem in Ba + . A significant improvement over earlier ab initio approaches is demonstrated and correlations are shown to have a large effect. A correct choice of g leads to simultaneous agreement between theory and experiment for three different classes of data, namely, quantum defects, intensity variation and the spin-orbit splitting.