Correlated-basis description of α-cluster and delocalized 0+ states in 16O

A five-body calculation of C-12+ n + n + p + p is performed to take a step towards solving an outstanding problem in nuclear theory: the simultaneous and accurate description of the ground and first excited 0(+) states of O-16. The interactions between the constituent particles are chosen consistently with the energies of bound subsystems, especially C-12+ n, C-12+ p, and the alpha particle. The five-body dynamics is solved with the stochastic variational method on correlated Gaussian basis functions. No restriction is imposed on the four-nucleon configurations except for the Pauli principle excluding the occupied orbits in C-12. The energies of both the ground and first excited states of O-16 are obtained in excellent agreement with experiment. Analysis of the wave functions indicates a spatially localized alpha-particle-like cluster structure for the excited state and a shell-model-like delocalized structure for the ground state.