Discovery of Mg-40, Al-42, and Al-43
November 21st, 2007 by mitch
(127 Views)
Baumann et al. have recently reported the discovery of three new isotopes 40Mg, 42Al, and 43Al. The discovery is notable for producing an isotope that neither the finite range droplet model (FRDM) nor the Hartree-Fock-Bogoliubov (HFB-8) predicted should be bound.
Of the 3 isotopes, the discovery of 42Al is an unexpected surprise and thusly the most fascinating. As we all know from undergraduate nuclear chemistry the Weizsäcker’s formula contains a pairing term (d) approximately equal to 34*A-3/4 MeV. The term increases the binding energy for an even number of protons (Z) and neutrons (N), decreases it for an odd Z and N, and of course is zero for an odd atomic number (A). 42Al contains 13-protons and 29-neutrons, lies on the extreme neutron-rich side, and thus was not predicted to exist in a bound state.
Theory can be seen to be in contradiction from experimental data as seen below.
 |
| Reprinted by permission from Macmillan Publishers Ltd: Nature 449, 1022 - 1024 (25 Oct 2007). |
To the immediate left of the 43Al dot is the collection of 42Al events. The 43Al event had a probability of ~2 x 10-3 of arising from the Al-42 cluster of events.The tantalizing conclusion of this work is that the neutron-drip line may reside further than even the next generation nuclear facilities could explore for Z>12.
Link to article: http://dx.doi.org/10.1038/nature06213
Mitch
on
No comments yet.