Editor's Summary

25 October 2007

The edge of stability

The limit of how many neutrons can be bound by a given number of protons — called the neutron drip line — is of fundamental importance in nuclear physics. It is unknown for all but the lightest elements, because of the complex interplay between single particle and collective quantum effects, but the detection of two new neutron-rich isotopes of magnesium and aluminium is a significant step towards establishing this limit. ⁴⁰Mg and ⁴²Al, predicted to be 'drip-line' nuclei on the edge of stability, were produced at the coupled cyclotron facility of the US National Superconducting Cyclotron Laboratory. The debut of ⁴²Al is the first experimental indication that the stability of very neutron-rich aluminium isotopes is enhanced relative to magnesium, and indicates that the neutron drip line may be farther from stable isotopes than expected. The findings suggest that the drip line may be beyond the reach of most current and projected nuclear science facilities for nuclei with atomic numbers over 12.

News and Views: Nuclear physics: Neutrons cross the line

For most atomic nuclei, the maximum number of neutrons that can be bound is unknown. The discovery of two neutron-rich nuclei — and the confirmed absence of others — might help solve this conundrum.

Paul-Henri Heenen

doi:10.1038/449992a

Full Text | PDF (187K)

Letter: Discovery of ⁴⁰Mg and ⁴²Al suggests neutron drip-line slant towards heavier isotopes

T. Baumann, A. M. Amthor, D. Bazin, B. A. Brown, C. M. Folden III, A. Gade, T. N. Ginter, M. Hausmann, M. Mato, D. J. Morrissey, M. Portillo, A. Schiller, B. M. Sherrill, A. Stolz, O. B. Tarasov & M. Thoennessen

doi:10.1038/nature06213

First paragraph | Full Text | PDF (495K)