Primary rainbow and Airy minima in ¹²C + ¹²C elastic scattering with families of non-monotonic potentials*

Abstract

The experimental differential cross section of the 12C + 12C elastic scattering over a wide laboratory energy scale 25 ⩽ E lab ⩽ 360 MeV are analyzed within the framework of the optical model (OM) using non-monotonic (NM) nucleus–nucleus potential. The real parts of the NM potentials are derived from the energy density functional (EDF) formalism with the sudden approximation embodying the Pauli exclusion principle and the imaginary parts are taken as phenomenology. The diffractive and the refractive scattering with Airy structures in the whole angular region of the 12C + 12C elastic scattering in the above mentioned energy range are found profoundly successful in OM with the NM nucleus–nucleus potentials in five of different potential families. All the families at lower energies converge at 240 MeV to the unique potential family starting with the EDF potential. This, in conjunction with our recent findings for the 16O + 16O system in Islam et al (2021 J. Phys. G 48 075109), not only verifies the Goldberg criterion for elimination of discrete potential ambiguities for NM potentials, but also establishes that this leads uniquely to the EDF family. The 90° excitation function is also successfully reproduced with extension using NM potentials. The near- and far-side (N/F) decomposition of total elastic scattering amplitude has also been studied using our NM potentials.

16O + 16O cluster states and their fusion to 32S: A non-monotonic potential description

“…The lowest bound molecular band is expected to have the simplest molecular dynamics and to serve as a key to understand the quasi-molecular bands in the SD and VD configurations of 32 S. Successes of the NM nucleus-nucleus potential have stimulated us to explore the 16 O + 16 O cluster bands and their fusion to 32 S in a simple OM using the NM potentials generated from the EDF theory of BCD. To do this we need good 16 O + 16 O interaction potentials, completely free of discrete ambiguities and, ideally, free of continuous ambiguities as well [28,29,31]. EDF-derived NM potentials are good at lower energies, being most accurate at the zero excitation energy E x = 0.0 MeV of the composite nucleus as detailed in [29].…”

“…To do this we need good 16 O + 16 O interaction potentials, completely free of discrete ambiguities and, ideally, free of continuous ambiguities as well [28,29,31]. EDF-derived NM potentials are good at lower energies, being most accurate at the zero excitation energy E x = 0.0 MeV of the composite nucleus as detailed in [29].…”

“…The CS data are analyzed using the code SFRESCO which incorporates the coupled-channels code FRESCO2.5 [57] and the χ 2 minimization code MINUIT [58]. Details of the fitting strategy are given in [10,28,29]. Special care has been taken to keep the imaginary part shallow enough [39,59] to contain the continuous ambiguities associated with the real-imaginary parts of the optical potential (OP) and to maintain adequate transparency of the scattering medium to support the refractive features including the nuclear rainbow.…”

“…The NM nucleus-nucleus potential has been found [28,29] to obey the Goldberg criterion [30] for eliminating high energy discrete ambiguities and also explicitly reveals the multiple potential families at lower incident energies.…”

“…The potential families [28,29,31] provide an excellent description of experimental data spanning a wide angular range. They are also [28,29] useful indicators of non-elastic processes and perform similarly in describing elastic scattering data.…”