Proton single-particle states in the neutron-rich 23F nucleus

The proton shell structure in neutron-rich fluorine 23 F was investigated using the in-beam gamma-ray spectroscopy technique via the proton transfer reaction onto the O-22 nucleus. We also measured the alpha inelastic scattering on F-23, the neutron knockout from F-24, and the two-nucleon knockout from Ne-25 using a cocktail secondary beam. By comparison of the population strengths for excited states in these reactions, we deduced the character of the excited states. The levels and gamma-decay scheme in F-23 were proposed based on de-excitation gamma-rays and the products of these reactions. We found that the 2268- and 4059-keV levels have strong proton single-particle nature of the s(1/2) and d(3/2) orbitals, respectively, by analysis of the population strengths and the angular distributions of the states. These single-particle states are located at higher excitation energies than the shell model predictions for the USD and SDPF-M interactions, which indicates that the centroid energy gaps for pi d(5/2)-pi s(1/2) and pi d(5/2)-pi d(3/2) are wider than predicted. (c) 2006 Elsevier B.V. All rights reserved.