A renormalized three-body model with zero-range potential is used to estimate the mean-square radii of three-body halo nuclei and molecular systems. The halo nuclei ($^6$He, $^{ 11}$Li, $^{ 14}$Be and $^{ 20}$C) are described as point-like inert cores and two neutrons. The molecular systems, with two helium atoms, are of the type $^4$He$_2-$X, where X$=^4$He, $^6$Li, $^7$Li, or $^{ 23}$Na. The estimations are compared with experimental data and realistic results.
Categories: nucl-th cond-mat physics.atm-clus