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.

The 44 Ar(d,p) 45 Ar neutron transfer reaction was performed at 10 A.MeV. Measured excitation energies, deduced angular momenta and spectroscopic factors of the states populated in 45 Ar are reported. A satisfactory description of these properties is achieved in the shell model framework using a new sdpf interaction. The model analysis is extended to more exotic even-Z nuclei down to 41 14 Si27 to study how collectivity impacts the low lying structure of N = 27 neutron-rich nuclei.