Reaction cross-sections and reduced strong absorption radii of nuclei in the vicinity of closed shells N = 20 and N = 28

International audienceEnergy integrated reaction cross-section measurements of around sixty neutron-rich nuclei covering the region of closed shells N = 20 and N = 28 were performed at intermediate energy (30-65 A . MeV) using direct method. In this experiment, silicon detectors were used as active targets. The reduced strong absorption radii, r02, for 19 new nuclei ($^{27}$F, $^{27,30}$Ne, $^{33}$Na, $^{28, 34-35}$Mg, $^{36-38}$Al, $^{38-40}$Si, $^{41-42}$P, $^{42-44}$S and $^{45}$Cl) are deduced for the first time. An additional 60 radii, also measured in this experiment, are compared to results from literature. A new quadratic parametrization is proposed for the nuclear radius as a function of the isospin in the region of closed shells N = 8 and N = 28. According to this parametrization, the skin effect is well reproduced and anomalous behaviour on the radii are observed in $^{23}$N, $^{29}$Ne, $^{33}$Na, $^{35}$Mg, $^{44}$S, $^{45}$Cl and $^{45}$Ar nuclei