Low-energy spectra of mirror mass-19 nuclei with a collective coupled-channel scattering model

The spectra of mass-19 nuclei are unusual and pose a challenge for theoretical models of their structure. Herein the Multi-Channel Algebraic Scattering (MCAS) method has been used with a collective (vibrational model) description of the low-excitation states of O-18 and Ne-18 to describe the spectra of four mass-19 nuclei, specifically the mirror pairs (O-19, Na-19) and (F-19, Ne-19). This coupled-channel approach allows for the effects of the Pauli principle to be included using non-local orthogonalizing pseudo-potentials. By the coupling of neutrons to the core nuclei, we obtain states in O-19 (a neutron coupled to O-18) and Ne-19 (a neutron coupled to Ne-18). Mirror symmetry and addition of the Coulomb interaction gives states in F-19 (a proton coupled to O-18) and Na-19 (a proton coupled to Ne-18). However, the same compound nuclei may be described as the coupling of more complicated nuclear clusters. We obtain the states in F-19 as the coupling of an alpha to N-15, as well as the coupling of H-3 to O-16. Similarly, states in Ne-19 have been obtained from the coupling of an alpha to O-15 and of the coupling of He-3 to O-16. Finally, as the method allows extraction of scattering matrices, it has been used to evaluate cross sections for the elastic scattering of low-energy neutrons from O-18 and of low-energy alpha particles from O-15.