Evidence for a dynamically refracted primary bow in weakly bound ${}^9$Be rainbow scattering from ${}^{16}$O

We present for the first time evidence for the existence of a dynamically refracted primary bow for ${}^9$Be+${}^{16}$O scattering. This is demonstrated through the use of coupled channel calculations with an extended double folding potential derived from the density-dependent effective two-body force and precise microscopic cluster wave functions for ${}^9$Be. The calculations reproduce the experimental Airy structure in ${}^9$Be+${}^{16}$O scattering well.It is found that coupling of a weakly bound ${}^9$Be nucleus to excited states plays the role of a booster lens, dynamically enhancing the refraction over the {\it static} refraction due to the Luneburg lens mean field potential between the ground states of ${}^9$Be and ${}^{16}$O.