Twice-magic metal makes its debut.
On Sept. 24, researchers at the Grand Accelerateur National d'Ions Lourds in Caen, France, announced that they have made the first sample of nickel-48. Ten days of bombarding a nickel target with a stable nickel isotope yielded two of the short-lived atoms.
What's so important about nickel-48? First of all, "it is doubly, magic," says team spokesman Bertram Blank of the Centre d'Etudes Nucleaires in Bordeaux-Gradignan, France.
A nucleus enjoys greater stability if it has "magic" numbers of protons or neutrons--that is, just enough to fill concentric shells of nuclear particles--theorists say. The number of neutrons, 20, and of protons, 28, in nickel-48 both fit the bill.
Only nine others of the roughly 2,500 known atomic nuclei are doubly magic, and nickel-48 stands out even in that exclusive crowd. While naturally occurring atoms have nearly equal numbers of neutrons and protons, nickel-48 weighs in with the greatest percentage excess of protons of any nucleus. Because it's rich in protons, which repel each other, but it fills its shells, the isotope teeters between disintegration and stability.
Researchers have long waited to test models of nuclear structure on such a substance. Blank says future experiments will explore whether nickel-48 emits a type of radioactivity predicted but never seen before--ejection of two protons at once.
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|Title Annotation:||isotope of nickel|
|Article Type:||Brief Article|
|Date:||Oct 23, 1999|
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