Mr. Smith's Science Classes

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Dr. Witek Nazarewicz draws the blueprint for what may just
prove to be a brand new element

Witek Nazarewiczis an explorer, of sorts. His
tools are math and physics, his terrain is the nuclear landscape, and his
mission is to find the "magic nuclei." He has recently come closer to his goal
by providing the mathematical calculations for what might turn out to be the
newest additions to the periodic table: elements 114, 116, and 118.

Dr. Nazarewicz is a theoretical physicist who lends his expertise to both the
University of Tennessee and the Oak Ridge National Laboratory. His specialty is
the nucleus, the bundle of neutrons and protons that serves as the nerve center
of all atoms and contains most of their mass. When the Curies discovered 100
years ago that not all nuclei are stable (radioactivity), a new era began for
science. Physicists began to wonder what were the limits of charge and mass for
a nucleus. By playing with the numbers of protons and neutrons, they could
synthesize elements in laboratories. But while naturally occurring elements are
long-lived, the unstable lab-created variety had much shorter lifetimes, quickly
falling victim to decay. Thus the challenge for theorists like Dr. Nazarewicz
was to draw some sort of blueprint to map out the uncharted territory of the
nuclear landscape (or "terra incognita," as he calls it) to create heavy
elements, or, as he says, "see how far you can go in atomic mass; how heavy you
can make the stuff." For the past several years, he and his colleagues from
Warsaw and Brussels have been designing mathematical models to do just that. As
it turns out, another group of physicists was conducting an experiment that
would fit those blueprints quite well.

Dr. Nazarewicz's illustration of the nuclear landscape, which compares the
region of unknown nuclei to unexplored territory in Africa (terra
incognita).

A New Addition to the Periodic Table? Maybe.

During November and December of 1998, scientists from theJoint Institute for Nuclear Research in Russia
and Lawrence Livermore Laboratory were busy running experiments to see just how
"heavy" they could go. For 40 days, they bombarded plutonium targets with
calcium ions, creating 10¹⁸collisions. Of all those, one decay chain
stood out as a candidate to be a new element, number 114. The chain had a much
longer lifetime than the last element, 112, discovered in 1996. When Dr.
Nazarewicz and his team heard of the project, they provided the experimentalists
with their mathematical models and found remarkable agreement between the theory
and experiment. In April of this year,another team from Lawrence Berkeley
National Laboratory and Oregon State Universityperformed similar
experiments, using lead targets and krypton ions. The results showed three decay
chains, indicating not only element 114 but elements 116 and 118 as well. Robert
Smolanczuk of Poland's Soltan Institute provided the initial theory calculations
for this work, which was also supported by the calculations by S. Cwiok
(Warsaw/JIHIR), Dr. Nazarewicz, and P.H. Heenen (Brussels/JIHIR).

Although he is quick to acknowledge the data are not 100 percent conclusive,
Dr. Nazarewicz is certainly encouraged by the evidence his work provides for the
possible existence of element 114. These are "calculations that greatly support
the identification made in experimental papers," he said. The work is being
chronicled in the scientific literature, as the experimental group submitted a
paper in March 1999 to Physical Review Letters, to be followed by another paper
by Dr. Nazarewicz's theory group. A second experimental paper, on a second
isotope of element 114, has also been submitted to Nature by the Dubna group.
The Berkeley/Oregon paper was submitted to the same journal in June 1999. Below
is what the periodic table looks like with the possible inclusion of elements
114, 116, and 118.

Gaining Ground on the "Magic Nuclei"

Dr. Nazarewicz explained that what makes this work so exciting is that it
demonstrates that scientists are getting closer to the superheavy "magic
nuclei," longest-lived super-heavy elements. Scientists began making predictions
about these elements some 30 years ago. In 1981, Bohrium (element 107) became
the first member of the superheavy class. Since then, Dr. Nazarewicz explained
that subsequent element discoveries are "slowly approaching greater shell
stability," as their lifetimes have gone from microseconds to several minutes.
As explained in the 1999 National Research Council report, Nuclear Physics: the
Core of Matter, the Fuel of Stars, "superheavies" are important because they
would provide "crucial information on relativistic effects in atomic physic and
quantum chemistry."

The superheavies represent the fourth period of radioactive element discovery
in scientific history. The first (1896-1940) was characterized by the Curies'
work and the discovery of polonium. The Manhattan Project marked the second
period (1940-1952), when plutonium became part of the periodic table. The third
period (1955-1974) witnessed a Cold War competition of sorts between Russian
laboratories at Dubna and American laboratories in Berkeley to discover new
elements. The fourth period (1974-1996) has been dominated by work in Darmstadt,
Germany, which has been responsible for six new elements since 1981. The last
three (110, 111, and 112) are still
unnamed, due to the "politics involved," Dr. Nazarewicz said. Because of
disputes over the proper name for these new elements, the International Union
for Pure and Applied Chemistry has devised a Latin system to give each a
temporary name based on its individual numbers. So for now, 114 is technically
ununquadium, 116 is ununhexium, and 118 is ununoctium.

Although more experimentation will be necessary to prove the elements'
existence, Dr. Nazarewicz will turn his attention back to drawing new blueprints
of the nuclear landscape in search of magic nuclei.

"I'm a theorist," he says with a laugh. "I don't smash atoms."

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