Spectroscopy of deeply bound orbitals in neutron-rich Ca isotopes

Li, P. J.*; Utsuno, Yutaka   ; Yoshida, Kazuki   ; 85 of others*

We report on the first measurement of unbound states in Ca and Ca, populated from Ca reactions. Orbital angular momentum assignments were extracted from momentum distributions calculated with the distorted wave impulse approximation (DWIA). The resonances at 5516(41) keV in Ca and 6000(250) keV in Ca indicate a significant = 3 component, providing the first experimental evidence for the single-particle strength of unbound hole states in the neutron-rich Ca isotopes. The observed excitation energies and cross-sections point towards extremely localized and well separated strength distributions, with some fragmentation for the orbital in Ca. These results are in good agreement with predictions from shell-model calculations using the effective GXPF1Bs interaction and ab initio calculations and diverge markedly from the experimental distributions in the nickel isotones at Z = 28.