An Elemental Discovery

The target was tiny--two-millionths of an ounce of a heavy, man-made isotope. The "bullets" were even smaller --atomic nuclei fired by an atom smasher. But the results of the experiment which were reported last week at a Washington meeting of the American Physical Society, made big news in the world of nuclear physics. A new chemical element, No. 105, has been created and identified.

After setting up sophisticated detectors to monitor their results, a team ol physicists led by Albert Ghiorso used the University of California's Lawrence Radiation Laboratory's heavy-ion linear accelerator (HILAC) to shoot nitrogen 15 nuclei with an energy level of 84 million electron volts at a submicroscopic bit of californium 249. Although a constant stream of nuclei was directed at the target, only about six collisions per hour produced atoms of the new element.

As the nuclei of the nitrogen 15 and californium 249 atoms met, they fused into a single nucleus containing a total of 260 neutrons and protons (four neutrons were shed in the process). Of these particles, 105 were protons, the positively charged particles that determine the atomic number of the element. Since there were 105 protons, the nucleus of the 105th element had been created.

Chemical Revolution. Ghiorso, Nuclear Chemist James Harris, Finnish Physicists Matti Nurmia and Kari Eskda, the same team that discovered element 104, suggested that the new element be named hahnium, in honor of Otto Hahn, the German chemist who in 1938 discovered nuclear fission. Ghiorso also took the occasion to disagree with a prior--and tentative --claim by Russian physicists that they had discovered element 105. The Lawrence team, he explained, had been unable to duplicate the Russian experiment, which used less sensitive equipment and produced uncertain results.

Whoever deserves the credit, the fact remains that scientists are synthesizing ever more complex elements, and coming closer to the day when they might create superheavy elements in the range of 110 (which would resemble platinum) to 114 (similar to lead). According to theory, they should be so long-lived that traces of them may still exist in their natural state on earth and the moon (scientists are looking for them in the lunar rocks brought back by Apollo). If they are ever found or--more likely--produced in the laboratory, says Ghiorso, "it would revolutionize chemistry. It would be the most fantastic thing in my lifetime."

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