U.S.-Russian Team May Have Created Ultra-Heavy Element

U.S.-Russian Team May Have Created Ultra-Heavy Element

By MALCOLM W. BROWNE

Friday, January 29, 1999

Collaborating Russian and American nuclear physicists believe they have created a new ultra-heavy element that may open the door to a host of new elements once considered impossible.

If confirmed, the achievement would mark the realization of efforts over a half century to reach a major goal of nuclear physics: to create an element far heavier than any in nature that would survive for long enough to permit scientific study.

Russian physicists announced the news over the last few weeks through e-mail to international physics laboratories, and the journal Science published a brief account of the work on Jan. 22.

The work to create the element, which has not been named, was conducted at the Joint Institute for Nuclear Research at Dubna, Russia, under the leadership of Dr. Yuri Oganessian, a nuclear physicist.

The American participants in the experiment, from Lawrence Livermore National Laboratory in California, said in interviews Thursday that they would have preferred to withhold the news until they had completed some calculations, but that the evidence for the creation of the element was very strong.

It appears, they said, that during a four-month bombardment from a big Russian cyclotron of a rare isotope, or form, of plutonium by atoms of a rare isotope of calcium, a single atom of the new element was created. The nucleus of a calcium projectile atom fused with the nucleus of a target plutonium atom to form an element containing 114 protons and about 184 neutrons in its nucleus. The resulting atom of Element 114 survived for about 30 seconds, they said, a long period compared with the decay rates of most other heavy man-made elements.

The pattern of radiation and nuclear fragments from the decaying atom matched the pattern predicted by theory for the decay of Element 114, the scientists said.

The creation of Element 114, if confirmed, would place science at the edge of the long-sought "island of stability," theoretically a range of fairly stable ultra-heavy artificial elements that physicists say may offer scientists a new palette of chemical elements unknown in nature.

The achievement, if confirmed by laboratories in Russia, the United States and Germany, where similar research has been done, would be a landmark in the course of nuclear discoveries that began in World War II with the creation of plutonium, the element used to destroy Nagasaki, Japan.

Of the 92 elements in the basic periodic table from hydrogen, the lightest, with only one proton in its nucleus, to uranium, the heaviest, with 92 protons, all but two elements, technetium and promethium, are found in nature.

Tiny amounts of plutonium have also been found in nature. But with that exception, all elements with proton numbers greater than the 92 of uranium must be made in laboratories, and with Element 114, 21 artificial elements have been made. (Element 113 is missing from the sequence.)

Many of the elements created since plutonium have found important uses in medicine, chemistry and even smoke detectors, which use the radioactive man- made element americium.

The possibility of creating a stable super-heavy element was first predicted in the 1940s by theorists who hypothesized a shell structure of protons and neutrons in large atomic nuclei, analogous to the shells of electrons orbiting atomic nuclei. They believed that nuclei with filled proton and neutron shells would be less likely to disintegrate radioactively than nuclei with partly filled shells.

But despite intense efforts by scientists in the United States, Russia and Europe in the intervening half century, the goal of making a super-heavy element within the island of stability was not achieved. A major problem was that when two atomic nuclei collide, they often combine energies to such high levels that the new composite nucleus instantly shakes itself apart.

The 18-member Dubna team, assisted by five American physicists, created the putative atom of Element 114, using a large cyclotron to hurl projectile atoms of calcium-48 at targets of plutonium-244. Both of these radioactive isotopes were provided for the experiment by Lawrence Livermore Laboratory.

The scientists have not announced their results in any formal publication, but the Russian contingent unveiled its data in e-mail with foreign nuclear physicists, including Albert Ghiorso, a leading nuclear experimentalist at Lawrence Berkeley National Laboratory in Calif.

Ghiorso is a longtime associate of Dr. Glenn T. Seaborg, the Nobel laureate who created plutonium. Ghiorso is credited as a co-creator of 12 artificial elements beyond uranium.

"I can't tell you how much I wish we at the Lawrence Berkeley Laboratory had been the ones to get Element 114," he said. "It's one of the greatest achievements in physics. But I'm overjoyed that someone has done it."

The 88-inch Berkeley cyclotron will be used to try to repeat the Dubna experiment, he said.

Dr. Ronald Lougheed and Dr. John N. Wild, two members of the Livermore team, said they would continue to work on the Russian cyclotron to confirm the discovery, but meanwhile were preparing a formal paper reporting the results.

Bill Richardson, who as secretary of energy is in charge of Livermore and other national physics laboratories hailed the work. "If confirmed, the synthesis of Element 114 will create an important new opportunity to study the physics of extremely heavy elements," he said.