J. S. Winfield

Characteristics of neutron-rich nuclei around shell closures N=20 and 28

Abstract The paper presents a review of experimental results obtained at GANIL and FLNR Dubna on the study of the particle stability of neutron-rich nuclei near the neutron drip line. Very recent data on mass measurements of neutron-rich nuclei in the range A =29–47 at GANIL and some characteristics of binding energies in this region are presented. Nuclear binding energies are very sensitive to the existence of shells and provide clear signatures of shell closures. Experiments have been mostly performed in cooperation GANIL–Orsay–Dubna–Řež–Bucharest–Liverpool.

Structure of from the (p, d) reaction in inverse kinematics

We have performed the Be reaction in inverse kinematics. The were detected in the SPEG spectrometer and the deuterons detected in a silicon array in coincidence. The yield to the first excited state of is greater than that to the ground state, and increases with angle. Strong population of the two-alpha plus two-neutron states near 6 MeV (in the two-centre shell-model description) is observed. The ultimate goal is to study the microscopic structure of from the extracted spectroscopic factors.

Study of subshell closure atN = 40 by Coulomb excitation

SummaryA Coulomb excitation experiment has been performed in order to study the subshell closure atN = 40 for neutron-rich nuclei. This subshell effect is thought to be enhanced when largeN/Z ratios are encountered. Therefore, theZ = 2868Ni is of particular interest in order to test this behaviour. Some experimental information is already available for68Ni at low excitation energy: a 0+2 isomer, a 2+ state and a long-lived 5- state. The high energy of the 2+ state suggests the shell closure though its reduced transition probabilityB(E2) has never been mesured. The nuclei68Ni,70,72Zn,76Ge have been produced in the fragmentation of a86Kr beam at 60 MeV/A. The selection of these secondary beams has been performed by LISE3 spectrometer at GANIL. Performances of the detector system “Château de Cristal” and preliminary results on reduced transition probabilitiesB(E2) are presented and discussed.

Study of 11Be structure via the p(11Be, 10Be)d reaction

The reaction 11Be(p,d)10Be has been studied for the first time, using a secondary 11Be beam of 35.3 MeV/nucleon. Angular distributions up to about 15cmo were measured by detecting 10Be in a spectrometer and coincident deuterons in a position sensitive silicon detector array. Preliminary analysis provides evidence for a large core excitation component in the structure of 11BeGS.

Experimental evidence of a v (1d5/2)2 component to the 12Be ground state

Data have been obtained on exclusive single neutron knockout cross sections from 12Be to study its ground state structure. Preliminary cross sections for the first (0.32 MeV, 1/2−) and second (1.78 MeV, 5/2+, unbound) excited states in 11Be have been obtained, giving evidence of significant admixtures of both v (1p 1/2)2 and v (1d 5/2)2 configurations in the ground state of 12Be.