Up to now, the number of particles on the surface of the nucleus involved in a pygmy resonance -- or the number of neutrons particularly affected by the ion impact -- was unknown.

Maybe 7,000 Scientists have long wondered whether there is a limit to the number of protons and neutrons that can be clustered together to form the nucleus of an atom.

The steep increase in charge radii beyond neutron number 32 poses challenges for nuclear models that explore forces between two and three nucleons. This trend is captured by density functional theory.