Island of inversion

An island of inversion is a region of the chart of nuclides that contains isotopes with a non-standard ordering of single particle levels in the nuclear shell model. Such an area was first described in 1975 by French physicists carrying out spectroscopic mass measurements of exotic isotopes of lithium and sodium. Since then further studies have shown that neutron-rich isotopes of five elements, ¹¹Li, ³¹Na, ³⁶Mg, ³⁸Si, and ⁴⁸Ca belong to one such region. Because there are 5 known islands of inversion, physicists have suggested renaming the phenomenon as an "archipelago of islands of shell breaking". Studies with the purpose of defining the edges of this region are still ongoing.