Detecting bubbles in exotic nuclei

The occurrence of a bubble, due to an inversion of s1/2 state with the state usually located above, is investigated. Proton bubbles in neutron-rich argon isotopes are optimal candidates. Pairing effects which can play against the bubble formation are evaluated. They cannot prevent bubble formation in very neutron-rich argon isotopes such as 68Ar. This pleads for a measurement of the charge density of neutron-rich argon isotopes in the forthcoming years, with the advent of electron scattering experiments in next generation exotic beam facilities such as FAIR or RIBF.