  We extend the work of Mishchenko et al. (2000) regarding the exact results of
the polarization effect, using the theory of Amic et al. (1997) to derive a
model prediction for the polarization coherent opposition effect at small
angles. Our extension is to assess the effect of circular polarized light, thus
completing exact derivation of the full M\"uller matrix for the semi infinite
slab of Rayleigh sized particles. We find the circular polarization peak is
narrower than the coherent backscattering intensity peak, and weaker in
intensity.
