The separation factor relationship for multicomponent isotope separation by centrifugation is a_ij=a_0^delta_M, where a_ij is the separation factor of the i-th isotope from the j-th, a_0 is the separation factor per unit mass difference, and delta_M is the molecular mass difference of the species. Can this relationship also be used for the thermal diffusion method? If not, what is an alternative relationship?