We report quantum Monte Carlo calculations of ground and low-lying excited states for nuclei using a realistic Hamiltonian containing the Argonne two-nucleon and Urbana IX three-nucleon potentials. The calculations begin with correlated eight-body wave functions that have a filled -like core and four p-shell nucleons coupled to the appropriate quantum numbers for the state of interest. After optimization, these variational wave functions are used as input to a Green’s function Monte Carlo calculation made with a new constrained path algorithm. We find that the Hamiltonian produces a ground state that is within 2 MeV of the experimental resonance, but the other eight-body energies are progressively worse as the neutron-proton asymmetry increases. The ground state is stable against breakup into subclusters, but the ground state is not. The excited state spectra are in fair agreement with experiment, with both the single-particle behavior of and and the collective rotational behavior of being reproduced. We also examine energy differences in the isomultiplets and isospin-mixing matrix elements in the excited states of Finally, we present densities, momentum distributions, and studies of the intrinsic shapes of these nuclei, with exhibiting a definite cluster structure.
- Received 7 February 2000
- Published 1 June 2000
© 2000 The American Physical Society