The masses of 31 neutron-rich nuclei in the range A = 29-47 have been measured. The precision of 19 masses has been significantly improved and 12 masses were measured for the first time. The neutron-rich Cl, S, and P isotopes are seen to exhibit a change in shell structure around N = 28. Comparison with shell model and relativistic mean field calculations demonstrate that the observed effects arise from deformed prolate ground state configurations associated with shape coexistence. Evidence for shape coexistence is provided by the observation of an isomer in 43S.

No abstract

The masses of 39 neutron-rich nuclei in the mass range 17 to 37 have been measured using a direct time-of-flight technique following the fragmentation of a 48 Ca beam at 55 MeV/nucleon. The masses of 29 ' 30 Ne, 34 -3 5Mg and 36 » 37 A1 are reported for the first time. The very neutron-rich nuclei, 31 ' 33 Na, are found to be 2-4 MeV less bound than previously believed. Comparison is made with recently available large scale shell model calculations encompassing the deformed A~32 nuclei. Conclusions are drawn regarding the extent of the region of deformation, which is found to include 30 Ne.

No abstract

No abstract