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Production of Nickel-48

Dateline: 02/14/00

By Alan Bruzel

Nuclear Magic Numbers

Just as atoms have distinctive configurations of orbiting electrons, so they have distinctive arrangements of nucleons (protons and neutrons) in their nuclei. Forces amongst these nucleons determine nuclear stability. Nuclear modeling calculations show the strongest nuclear binding forces – and therefore the most stable nuclei – should occur in nuclei where there are a magic number (2, 8, 20, 28, 50, 82, or 126) of either protons or neutrons.

Doubly Magic Nuclei

These are, quite simply, nuclei containing protons and neutrons that are both magic numbers. For example, the helium-4 nucleus, with two protons and two neutrons, is doubly magic and is quite a stable entity. But being doubly magic does not of itself guarantee stability; the isotope nickel-56 (28 protons and 28 neutrons) is not stable (half-life of six days).

What Is Special about Nickel-48?

The lighter elements have relatively equal numbers of protons and neutrons. (Hydrogen-1 is exempted, as it has no neutrons.) As nuclei increase in size, they require many more neutrons than they have protons in order to effectively maintain their stability. It might be educational to fashion a neutron poor nucleus, and, as an added attraction, arrange for it to be doubly magic. Here, we could examine a nucleus that inherited both a neutron deficient instability and a potential double magic stability.

Nickel has an atomic number of 28; it therefore already possesses a magic number of protons. (The common, stable nickel isotope nickel-58, with a natural abundance of 68 atom %, has 28 protons and 30 neutrons.) A nickel nucleus with only twenty neutrons (another magic number) yields a nucleus both neutron poor and doubly magic: nickel-48.

In September 1999, scientists at the Grand Accélérateur National d’Ions Lourds succeeded in creating four nuclei of nickel-48 (along with some chromium-42, iron-45, and nickel-49 nuclei and billions of other, less interesting, collision particles) by smashing nickel-58 nuclei into a natural nickel target. The experimental results placed a lower limit for the half-life of nickel-48 at one-half of a microsecond (rather lengthy for a neutron deficient nucleus) and opened the possibility that nickel-48 may break down via two-proton radioactive decay, a theoretical conjecture thus far unobserved.

What the Web Has to Say about:
Nickel-48

An International Breakthrough: The Discovery of Nickel-48 at GANIL
Press release from the Centre National de la Recherche Scientifique describes identification of novel nickel nucleus at the Grand Accélérateur National d’Ions Lourds.

A World First: The Discovery of Nickel-48 at GANIL
Press release from the Commissariat à l'Énergie Atomique.

Carbon Burning, Silicon Burning, and Magic
Nuclear reactions in stars. From Lee Schroeder's Dark Matter and Other Elementary Particles.

Discovery of Doubly Magic ⁴⁸Ni
Physical Review Letters abstract by Bertram Blank et al.

Double Magic for New Nickel Nucleus
Significance of production of nickel-48 nucleus. Article by Adrian Cho, InSCIght magazine.

Glenn Seaborg: A Man in His Element
Biography of Glenn Seaborg includes his quest for synthesizing stable nuclei. From Douglas Page, Science Spectra magazine.

Holifield Facility Newsletter
Proposal to study the magic nucleus, tin-100. From the Holifield Radioactive Ion Beam Facility, Oak Ridge National Laboratory.

Nuclear Physics
Arrangements of protons and neutrons in nuclei. From the Modern Physics course of Peter Suranyi, University of Cincinnati.

Nuclear Structure Studies
Experimental approaches to understand magic nuclei. From The Institute of Physical and Chemical Research (RIKEN).

On the Road to Double Magic Nickel-48
Discovery of neutron deficient isotopes. From the Gesellschaft für Schwerionenforschung.

Scientific Program
Research involving more doubly magic nuclei: nickel-78 and lead-208. From the Department of Physics, Katholieke Universiteit Leuven.

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