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The Sciences

Physicists Extend the Periodic Table

Two new elements hint at an impending breakthrough in creating novel forms of matter that will test our understanding of atomic behavior.

By Alex StoneMarch 12, 2004 6:00 AM

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Nuclear physicists have long suspected the existence of atoms far heavier than any yet discovered, but they lacked the technology needed to synthesize them. Now, a joint American-Russian team has found two new elements—numbers 113 and 115 on the periodic table—hinting at an impending breakthrough in creating novel forms of matter that will test our understanding of atomic behavior.

Ultra-heavy elements tend to disintegrate almost as soon as they are created. The two new ones, however, appear to be the first of a long-sought family of relatively long-lived atoms. “You’re getting to a region where it looks like there is enhanced stability,” says Joshua Patin of Lawrence Livermore National Laboratories in California, chief data analyst for the collaborative project. To find these elements he and colleagues at Livermore and Russia’s Joint Institute for Nuclear Research collided ions (charged atoms) with other, target atoms in a cyclotron, a machine that accelerates the nuclei to high speeds with a magnetic field. The researchers bombarded radioactive americium-243 with calclium-48, shooting one trillion calcium atoms per second at the americium target, hoping that occasionally the atoms would stick together to form something new. After running cyclotron day and night for a month, Patin and company produced four atoms each of the new elements, enough to study how they decay.

Element 115 lives for 1/100,000^th of a second before breaking down into element 113, which in turn decays after a little over a second. In the world of heavy elements those seemingly brief lifetimes are an eternity. This discovery confirms a long-held theory in nuclear physics that there is a region of enhanced stability at the margin of the periodic table. And for each new element that is discovered, there are potentially numerous undiscovered isotopes (different versions of the same element), some of which could be very stable. Next the team will shoot for elements 117 and 118. “You can consider this region of the chart as a puzzle,” says Patin. “We get pieces of the puzzle, but there are a lot of isotopes of recently discovered elements that have not been seen.”

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