Evidence for core excitation in single - particle states of 19

We present an experimental study of Na states in the excitation energy range between 2 and 3 MeV. The presence of Na single-particle levels at these energies was first predicted by a microscopic cluster model and then experimentally confirmed by measuring the elastic and inelastic scattering of a 66 MeV Ne radioactive beam on a (CH2)n target. The H( Ne,p)Ne(g.s.) and H(Ne,p’)Ne*(2, 1.887 MeV) cross sections have been obtained in the laboratory angular range θlab = 6.1 −18.4 and analyzed by using the R-matrix method. Two new states in Na have been observed at centre of mass energies Ec.m. = 2.78± 0.01 MeV and 3.09± 0.05 MeV. Both resonances exhibit large widths in the Ne(2)+p channel, and low branching ratios into the elastic channel. The reduced proton widths confirm the single-particle nature of these states, with a Ne(2)+p structure.