LONG-RANGE POTENTIALS FOR 2 NA(3P) ATOMS INCLUDING IONIC COVALENT INTERACTION AND FINE-STRUCTURE - APPLICATION TO 2-COLOR PHOTOASSOCIATION SPECTROSCOPY

In the framework of ab initio pseudopotential calculations, a method i s presented to compute an effective spin-orbit Hamiltonian within a no northogonal diabatic representation separating the ionic and covalent subspaces. The resulting Hund's case c adiabatic curves display long r ange structures. We predict that a small (approximate to 1 cm(-1)) fin e-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 exp eriments using cold atoms.