Lawrence Berkeley National Laboratory

In a recent experiment, carried out at the Radioactive Isotope Beam Factory/RIKEN, the F25(p,2p)O24 reaction was studied at 270 MeV/A in inverse kinematics. Derived spectroscopic factors suggest that the effective core of F25 significantly differs from a free O24 nucleus. We interpret these results within the particle-rotor model and show that the experimental level scheme of F25 can be understood in the rotation-aligned coupling scheme with its 5/21+ ground state as the bandhead of a decoupled band. The excitation energies of the observed 1/21+ and 9/21+ states correlate strongly with the rotational energy of the effective core, seen by the odd proton, and allow us to estimate its 2+ energy at ≈3.2MeV and a moderate quadrupole deformation ϵ2≈0.15. The measured fragmentation of the πd5/2 single-particle strength is discussed, and some further experiments suggested.