Similarity between nuclear rainbow and meteorological rainbow - evidence for nuclear ripples -
We present evidence for the nuclear ripples superimposed on the Airy structure of the nuclear rainbow, which is similar to the meteorological rainbow. The mechanism of the nuclear ripples is also similar to that of the meteorological rainbow, which is caused by the interference between the externally reflective waves and refractive waves. The nuclear ripple structure was confirmed by analyzing the elastic angular distribution in $^{16}\mathrm{O}+^{12}\mathrm{C}$ rainbow scattering at ${E}_{L}=115.9$ MeV using the coupled channels method by taking account of coupling to the excited states of $^{12}\mathrm{C}$ and $^{16}\mathrm{O}$ with a double folding model derived from a density-dependent effective nucleon-nucleon force with realistic wave functions for $^{12}\mathrm{C}$ and $^{16}\mathrm{O}$. The coupling to the excited states plays the role of creating the external reflection.