Physical Sciences

The two-proton knockout reaction Be9(Ti54,Ca52+γ) has been studied at 72 MeV/nucleon. Besides the strong feeding of the Ca52 ground state, the only other sizeable cross section proceeds to a 3- level at 3.9 MeV. There is no measurable direct yield to the first excited 2+ state at 2.6 MeV. The results illustrate the potential of such direct reactions for exploring cross-shell proton excitations in neutron-rich nuclei and confirms the doubly-magic nature of Ca52. © 2006 The American Physical Society.