zz from New York Times

By JAMES GLANZ
Published: April 6, 2010

A team of Russian and American scientists has discovered a new element that
has long stood as a missing link among the heaviest bits of atomic matter
ever produced. The element, still nameless, appears to point the way toward a
brew of still more massive elements with chemical properties no one can
predict.

The team produced six atoms of the element by smashing together isotopes
of calcium and a radioactive element called berkelium in a particle accelerator
about 75 miles north of Moscow on the Volga River, according to a paper that
has been accepted for publication at the journal Physical Review Letters.

Data collected by the team seem to support what theorists have long
suspected: that as newly created elements become heavier and heavier they
will eventually become much more stable and longer-lived than the fleeting
bits of artificially produced matter seen so far.

If the trend continues toward a theorized “island of stability” at higher
masses, said Dawn A. Shaughnessy, a chemist at Lawrence Livermore National
Laboratory in California who is on the team, the work could generate an array
of strange new materials with as yet unimagined scientific and practical uses.

By scientific custom, if the latest discovery is confirmed elsewhere, the
element will receive an official name and take its place in the periodic table of
the elements, the checkerboard that begins with hydrogen, helium and
lithium and hangs on the walls of science classrooms and research labs the
world over.

“For a chemist, it’s so fundamentally cool” to fill a square in that table, said
Dr. Shaughnessy, who was much less forthcoming about what the element
might eventually be called. A name based on a laboratory or someone
involved in the find is considered one of the highest honors in science.
Berkelium, for example, was first synthesized at the University of California,
Berkeley.

“We’ve never discussed names because it’s sort of like bad karma,” she said.
“It’s like talking about a no-hitter during the no-hitter. We’ve never spoken
of it aloud.”

Other researchers were equally circumspect, even when invited to suggest a
whimsical temporary moniker for the element. “Naming elements is a serious
question, in fact,” said Yuri Oganessian, a nuclear physicist at the Joint
Institute for Nuclear Research in Dubna, Russia, and the lead author on the
paper. “This takes years.”

Various aspects of the work were done at the particle accelerator in Dubna;
the Livermore lab; Oak Ridge National Laboratory and Vanderbilt University in
Tennessee; the University of Nevada, Las Vegas; and the Research Institute of
Atomic Reactors in Dimitrovgrad, Russia.

For the moment, the discovery will be known as ununseptium, a very
unwhimsical Latinate placeholder that refers to the element’s atomic number,
117.

“I think they have an excellent convincing case for the first observation of
element 117; most everything has fallen into line very well,” said Walter D.
Loveland, a professor of chemistry at Oregon State University who was not
involved in the work.

Elements are assigned an atomic number according to the number of protons
— comparatively heavy particles with a positive electric charge — in their
nuclei. Hydrogen has one proton, helium has two, and uranium has 92, the
most in any atom known to occur naturally. Various numbers of charge-free
neutrons add to the nuclear mass of atoms but do not affect the atomic
number.

As researchers have artificially created heavier and heavier elements, those
elements have had briefer and briefer lifetimes — the time it takes for
unstable elements to decay by processes like spontaneous fission of the
nucleus. Then, as the elements got still heavier, the lifetimes started climbing
again, said Joseph Hamilton, a physicist at Vanderbilt who is on the team.

The reason may be that the elements are approaching a theorized “island of
stability” at still higher masses, where the lifetimes could go from fractions of
a second to days or even years, Dr. Hamilton said.

In recent years, scientists have created several new elements at the Dubna
accelerator, called a cyclotron, by smacking calcium into targets containing
heavier radioactive elements that are rich in neutrons — a technique
developed by Dr. Oganessian.

Because calcium contains 20 protons, simple math indicates scientists would
have to fire the calcium at something with 97 protons — berkelium — to
produce ununseptium, element 117.

Berkelium is mighty hard to come by, but a research nuclear reactor at Oak
Ridge produced about 20 milligrams of highly purified berkelium and sent it
to Russia, where the substance was bombarded for five months late last year
and early this year.

An analysis of decay products from the accelerator indicated that the team
had produced a scant six atoms of ununseptium. But that was enough to title
the paper, “Synthesis of a new element with atomic number Z=117.”

That is about the closest thing to “Eureka!” that the dry conventions of
scientific publication will allow. The new atoms and their decay products
displayed the trend toward longer lifetimes seen in past discoveries of such
heavy elements. The largest atomic number so far created is 118, also at the
Dubna accelerator.

Five of the six new atoms contained 176 neutrons to go with their 117
protons, while one atom contained 177 neutrons, said Jim Roberto, a
physicist at Oak Ridge on the project.

Atomic nuclei can be thought of as concentric shells of protons and neutrons.
The most stable nuclei occur when the outermost shells are filled. Some
theories predict this will happen with 184 neutrons and either 120 or 126
protons: the presumed center of the island of stability.

What happens beyond that point is anyone’s guess, said Kenton Moody, a
radiochemist on the team at Livermore. “The question we’re trying to answer
is, ‘Does the periodic table come to an end, and if so, where does it end?’ ”
Dr. Moody said.
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FROM 76.114.110.*