Splitting of the tetrahedral 87Rb- and 39K- nuclear magnetic resonance lines in these materials was analyzed in terms of alkali-cation vacancy mechanisms. The calculations indicated the presence of vacancies only in tetrahedral positions. The inter-atomic potentials between alkali cations and fullerene molecules accounted satisfactorily for the temperature dependence of the position of the distorted line.

M.Apostol, C.Goze, F.Rachdi, M.Mehring, J.E.Fischer: Solid State Communications, 1996, 98[3], 253-7