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 ^18 O and ^18 Ne to describe the spectra of four mass-19 nuclei, specifically the mirror pairs ( ^19 O, ^19 Na) and ( ^19 F, ^19 Ne). 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 ^19 O (a neutron coupled to ^18 O) and ^19 Ne (a neutron coupled to ^18 Ne). Mirror symmetry and addition of the Coulomb interaction gives states in ^19 F (a proton coupled to ^18 O) and ^19 Na (a proton coupled to ^18 Ne). However, the same compound nuclei may be described as the coupling of more complicated nuclear clusters. We obtain the states in ^19 F as the coupling of an α to ^15 N, as well as the coupling of ^3 H to ^16 O. Similarly, states in ^19 Ne have been obtained from the coupling of an α to ^15 O and of the coupling of ^3 He to ^16 O. 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 ^18 O and of low-energy α particles from ^15 O.