The Search for New Elements: the Projects of Today in a Larger Perspective

Abstract

The search for new elements is based on the irradiation of heavy element targets with heavy ions followed by identification through physical or chemical methods. Success seems assured for the production and identification of short-lived elements immediately beyond the heaviest presently known. Predictions indicate that still heavier elements, the superheavy elements as part of an "island of stability", would have sufficient stability to allow their identification; however, there is no equal assurance that nuclear reactions suitable for their synthesis can be found.The chemical properties of a wide range of such prospective new elements have been predicted, in many cases in rather extensive detail. Special considerations related to their high atomic numbers suggest interesting differences between the chemical properties of these heavy elements and their lighter homologs.Chemical separation schemes for the identification of superheavy elements have been devised and applied to heavy targets irradiated with heavy ions. While there may be some positive indications of such identification in experiments performed at Dubna, experiments at Berkeley have given negative results.In the Berkeley experiments the yields of a broad range of isotopes of the known elements in the separated chemical fractions have been determined. The resulting distribution of products formed in the irradiation of uranium with krypton ions suggest some interesting new reaction mechanisms.