Long range potentials for two Na(3p) atoms including ionic covalent interaction and fine structure: Application to two-color photoassociation spectroscopy

In the framework of ab initio pseudopotential calculations, a method is presented to compute an effective spin-orbit Hamiltonian within a nonorthogonal diabatic representation separating the ionic and covalent subspaces. The resulting Hund's case c adiabatic curves display long range structures. We predict that a small (approximate to 1 cm(-1)) fine-structure splitting of an ionic (3) Pi(u) curve is manifested in the spectrum of the excited Na-2 molecule slightly below the (3p P-2(1/2) + 3p P-2(1/2)) asymptote as a series of well identified quadruplets. They should be observed in two-color photoassociation spectroscopy experiments using cold atoms.