Further evidence for a dynamically generated secondary bow in $^{13}$C+$^{12}$C rainbow scattering

TL;DR

This paper confirms the existence of a secondary rainbow in 13C+12C nuclear scattering, demonstrating it is generated dynamically through coupling to an excited state of 12C, using an extended folding model and microscopic wave functions.

Contribution

It provides the first evidence of a secondary rainbow in 13C+12C scattering, highlighting the role of coupling to the 12C 2+ excited state and the importance of the Y2 reorientation term.

Findings

Secondary bow confirmed at 70° angle.

Coupling to 12C 2+ state generates the secondary bow.

Y2 term is crucial for secondary bow formation.

Abstract

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.