Unresolved puzzles in exotic nuclei (Vol. 49, No. 3)

Closed points are matter radii extracted from experiments for isotopes of Helium (diamonds), Lithium (squares), and Beryllium (triangles)

A new review highlights the historical developments in our understanding of the nuclear structure of unstable and unbound forms of helium, lithium and beryllium

Research into the origin of elements is still of great interest. Many unstable atomic nuclei live long enough to be able to serve as targets for further nuclear reactions—especially in hot environments like the interior of stars. And some of the research with exotic nuclei is, for instance, related to nuclear astrophysics. In this review published recently, the author discusses the structure of unstable and unbound forms of Helium, Lithium, and Beryllium nuclei that have unusually large neutron to proton ratios—dubbed ‘exotic’ light nuclei. The author offers an account of historical milestones in measurements and the interpretation of results pertaining to these nuclei. The author also delineates some of the unresolved puzzles concerning the connection between microscopic structure and the values of quantities that are observable experimentally-- particularly the interplay between energies, widths or strengths and microscopic structure. For example, physicists have yet to resolve what is the occupancy of an orbital, called 2s1/2, in the ground state of beryllium-12? Or what is the nature of the unbound ground state of helium-10?

H. T. Fortune, Structure of exotic light nuclei: Z = 2, 3, 4, Eur. Phys. J. A, 54, 51 (2018)