Reaction cross-section and reduced strong absorption radius measurements of neutron-rich nuclei in the vicinity of closed shells N=20 and N=28

The energy-integrated reaction cross-sections of several neutron-rich nuclei (N17-22, O19-24, F21-27, Ne23-30, Na26-33, Mg28-35, Al31-38, Si33-40, (36-42)p, S39-44, Cl42-45, Ar-45,Ar-46), measured at intermediate energy (30-65 A MeV), via direct method, are presented. Silicon detectors have been used as the active target as well as for particles identification. The reduced strong absorption radii r(0)(2) are extracted and compared to the data available from the literature. New measurements for 19 nuclei (F-27, Ne-27,Ne-30, Na-33, (28,34-35)mg, Al36-38, Si38-40, P41-42, S42-44, Cl-45) are revealed. From the study of the isospin dependence of the reduced strong absorption radius, a new quadratic parameterisation of the nuclear radii in the closed shell regions N = 8 and N = 28, is proposed. According to this parameterisation, the proton/neutron rich nuclei skin effect is well described and a new anomalous structure: halo-structure or large deformation is suggested for Mg-35 and S-44 nuclei. (c) 2006 Elsevier B.V. All rights reserved