SHALLOWS OFF THE ISLAND OF STABILITY - Dubna Physicists Synthesize 106th Element on Mendeleyev's Periodic Table

Author: B. Konovalov

SHALLOWS OFF THE ISLAND OF STABILITY - Dubna Physicists Synthesize 106th Element on Mendeleyev's Periodic Table. (By B. Konovalov, Izvestia's science commentator. Izvestia, Nov. 5, p. 3. 1,800 words. Abstract:) Between 1962 and 1970. scientists succeeded in creating the transuranium elements with atomic numbers of 102 through 105. Thereafter they ran up against a blank wall. It became increasingly hard to obtain heavier and heavier target atoms from which to synthesize new elements, and, once in hand, they were radioactive and difficult to control. Physicists then attempted to bombard somewhat lighter targets with heavier "ammunition, " but this approach, too. proved unsuccessful when target and projectile failed to fuse. American researchers at Berkeley's Lawrence Laboratory experimentally verified predictions to this effect and concluded that the light-weight target method was not very promising. They therefore selected element 98, californium, as a target and oxygen ions as projectiles and proceeded to become bogged down in difficulties.

At the nuclear reactions laboratory of the Joint Nuclear Research Institute in Dubna, Doctor Yu. Ts. Oganesyan harbored reservations about the Americans' conclusion. Last summer his group demonstrated that light targets and heavy projectiles could be made to combine. First they produced nuclei of element 100 by this method and then several new isotopes of element 104. In a concerted effort the scientists began surmounting one obstacle after another in their quest for the as yet elusive number 106.

Engineer Yu. P. Tretyakov designed a unique source of ions of solid substances. Previously everyone had been using ions of gaseous substances, but the Dubna team wanted to bombard their targets with ions of titanium and chromium, which are virtually impossible to gasify. Mechanical engineer V. M. Plotko created a special device to "photograph" the 106th element. It consisted of two concentric cylinders with a target of lead nuclei deposited on the surface of the inner one. The outer cylinder had an aperture to ...

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