One-neutron removal reactions on Al isotopes around the N = 20 shell closure.

The one-neutron removal cross sections of neutron-rich Al isotopes and longitudinal momentum distributions of the residues have been measured for A = 33 to 36 at relativistic energies (≈900 MeV/u). The inclusive data have been interpreted within the eikonal approximation. The evolution of the single-particle occupancy in the ground state of 33,34,35A1 has been studied and compared with shell model predictions. The inferred 2s1/2 neutron occupancy in the 33A1 ground-state wave function is 20% to 40% lower than the predicted one. The inclusive data do not exclude the presence of intruder states. Some intruder / = 1 occupancy is found in 34A1, similarly to 33Mg. The single-particle 1 f7/2 occupancy shows a gradual increase at N = 22. Correspondingly, a decrease of the lrf3/2 strength has been observed. [ABSTRACT FROM AUTHOR]