Matter radii and wave function admixtures in 2n halo nuclei

In a simple potential model, we have computed matter radii for several 2n halo nuclei. Results are used to estimate wave function admixtures for these nuclei. Comparison is made with experimental and other calculated values. We propose a tighter limit on the binding energy of B-19: B-2n = 0.55(-0.16)(+0.20) replacing the previous value of 0.5(4) MeV.