  The existence of a secondary bow is confirmed for 13C+12C nuclear rainbow
scattering in addition to the 16O+12C system. This is found by studying the
experimental angular distribution of 13C+12C scattering at the incident 13C
energy $E_L$=250 MeV with an extended double folding (EDF) model that describes
all the diagonal and off-diagonal coupling potentials derived from the
microscopic wave functions for 12C using a density-dependent nucleon-nucleon
force. The Airy minimum at \theta$ $\approx$70$^\circ$, which is not reproduced
by a conventional folding potential, is revealed to be a secondary bow
generated dynamically by a coupling to the excited state 2+ (4.44 MeV) of 12C.
The essential importance of the quadruple {\it Y2} term (reorientation term) of
potential of the excited state 2+ of 12C for the emergence of a secondary bow
is found. The mechanism of the secondary bow is intuitively explained by
showing how the trajectories are refracted dynamically into the classically
forbidden angular region beyond the rainbow angle of the primary rainbow.
