Spin-orbit and spin-spin couplings in He2 and He2-

The spin-orbit and the spin-spin coupling constants of the (4)Pi(g) state of the He-2(-) ion, of the parent a(3)Sigma(u)(+), and of the b(3)Pi(g) states of He-2 have been evaluated by a multireference configuration interaction method. The theoretical spin-spin splittings of the a(3)Sigma(u)(+) state and the R-dependent spin-spin function are found to be in excellent agreement with experiment, with deviations in the range of a few MHz. The theoretical spin-orbit constants and splittings of the b(3)Pi(g) state are larger than the experimental values by about 370 MHz. The spinorbit coupling constant of the (4)Pi(g) state of He-2(-) is estimated to be three times smaller than in the b(3)Pi(g) state, but one of the intramultiplet off-diagonal spin-spin interactions is predicted to give a large contribution to the fine structure of the metastable ion. The theoretical fine structure constants for the He-2(-) ion are expected to aid future spectroscopic investigations of the fine structure splittings of the negative ion.