The N = 28 shell closure has been investigated via the 46Ar(d,p)47Ar transfer reaction in inverse kinematics. Energies and spectroscopic factors of the neutron p(3/2), p(1/2), and f(5/2) states in 47Ar were determined and compared to those of the 49Ca isotone. We deduced a reduction of the N = 28 gap by 330(90) keV and spin-orbit weakenings of approximately 10(2) and 45(10)% for the f and p states, respectively. Such large variations for the f and p spin-orbit splittings could be accounted for by the proton-neutron tensor force and by the density dependence of the spin-orbit interaction, respectively. This contrasts with the picture of the spin-orbit interaction as a surface term only.

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The reaction cross section for 8 B and 7 Be and the breakup cross section for 8 B on silicon have been measured for incident energies between 10 and 40 MeV/nucleon with a stack of silicon detectors. Secondary 8 B and 7 Be beams were obtained by use of the LISE spectrometer at GANIL. The stack of silicon detectors had the multiple purpose of slowing down the incident secondary beams, identifying the reaction products, and measuring their energy. The separate contributions of diffraction dissociation and absorption to the breakup have been determined. The parallel momentum distribution of 7 Be resulting from the breakup of 8 B has also been determined. The data are compared to theoretical calculations. ͓S0556-2813͑96͒06009-8͔

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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.