EFFECTS OF OFF-DIAGONAL ELECTRON-ELECTRON INTERACTIONS ON EXCITON ENERGIES IN C-60

Since the neighboring pi orbits in C-60 are well overlapped, the off-d iagonal part of electron interaction plays an important role. In this paper, the effects of the off-diagonal electron interactions on the ex citon energies in C-60 are studied by using the single configuration i nteraction approach. It is found that the binding energies of the low- lying singlet and triplet excitons depend sensitively upon the off-dia gonal interactions which compete against the diagonal interactions and suppress the binding of the excitons. The implication of these featur es is discussed.