Low-lying collective states in neutron-rich oxygen isotopes via proton scattering ☆

Abstract Proton elastic and inelastic scattering angular distributions to the 2 + 1 and the 3 − 1 states for the neutron-rich nucleus 20 O were measured with a secondary beam using the MUST silicon strip detector array. Data for 18 O were also obtained for comparison. A phenomenological analysis has been used to deduce the deformation parameters β p,p′ for the collective excitations. Matter and transition densities were generated from self-consistent QRPA calculations. DWBA calculations using microscopic optical potentials obtained with these densities and the JLM interaction are compared to the data. The isovector character of the 2 + 1 state in 20 O is confirmed and predictions are discussed for the properties of the heavier neutron-rich oxygen isotopes.