QUANTUM MONTE-CARLO CALCULATIONS OF NUCLEI WITH A-LESS-THAN-OR-EQUAL-TO-7

We report quantum Monte Carlo calculations of ground and low-lying exc ited states for nuclei with A less than or equal to 7 using a realisti c Hamiltonian containing the Argonne upsilon(18) two-nucleon and Urban a IX three-nucleon potentials. A detailed description of the Green's-f unction Monte Carlo algorithm for systems with state-dependent potenti als is given and a number of tests of its convergence and accuracy are performed. We find that the Hamiltonian being used results in ground states of both Li-6 and Li-7 that are stable against breakup into subc lusters, but somewhat underbound compared to experiment. We also have results for He-6, He-7, and their isobaric analogs. The known excitati on spectra of all these nuclei are reproduced reasonably well and we p redict a number of excited states in He-6 and He-7. We also present sp in-polarized one-body and several different two-body density distribut ions. These are the first microscopic calculations that directly produ ce nuclear shell structure from realistic interactions that fit NAI sc attering data.