Figure 1

Difference $\Delta r_{np}$ between the rms radii of the neutron and proton distributions deduced from the antiprotonic atom x-ray data as a function of $I=(N-Z)/A$ (open points with indicated statistical errors, [2]). Full points show the droplet model predictions for the same isotopes as measured in the experiment. The line is a fit to the experimental data: $\Delta r_{np}=(-0.03\pm 0.020)+(0.90\pm 0.15)I\mathrm{fm}$.Reuse & Permissions