A relationship between the measurable monomer-monomer structure factor, and
the centre-of-mass (CM) structure factor of dilute or semi-dilute polymer
solutions is derived from Ornstein-Zernike relations within the ``polymer
reference interaction site model'' (PRISM) formalism, by considering the CM of
each polymer as an auxiliary site and neglecting direct correlations between
the latter and the CM and monomers of neighbouring polymers. The predictions
agree well with Monte Carlo data for self-avoiding walk polymers, and are
considerably more accurate than the predictions of simple factorization
approximations.Comment: uses eps.cls, v2 is close to final published versio