Creating superheavy elements

Journal Article · Mon May 01 00:00:00 EDT 1989 · Scientific American; (USA)

DOI:https://doi.org/10.1038/scientificamerican0589-66· OSTI ID:6481060

Armbruster, P; Muenzenberg, G ^[1]

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1. Institute for Heavy-Ion Research, Darmstadt (West Germany)

During the past 20 years physicists around the world have been engaged in the task of producing superheavy elements. At the Institute for Heavy-Ion Research in Darmstadt the authors have met with some success, synthesizing the nuclei of elements 107, 108 and 109. These nuclei lie beyond the 106-proton threshold that marked the limits of previous techniques for creating and identifying heavy elements. Experimental mass measurements, followed up by theory, show that the new elements owe their stability to the microscopic arrangement of their protons and neutrons rather than the macroscopic properties that stabilize lighter nuclei. On the other hand the authors have met with problems that have thus far prevented them from reaching the goals set in the late 1960's, when elements up to 114 seemed within reach. Working to overcome obstacles to further progress, however, has deepened our understanding of nuclear structure and of the dynamics of fusion reactions between nuclei. Nucleosynthesis has come a long way from the earliest years when elements not found in nature were created in nuclear reactors. Physicists have employed ever-heavier projectiles to bombard target atoms; the latest development is cold fusion, which masses and bombardment energies are carefully chosen to minimize the excitation of newly formed nuclei. In the course of their work early ideas about how to synthesize superheavy elements have almost all turned out to be wrong: the nuclei of the elements that can be synthesized are deformed and not, as postulated in 1966, spherical. In the fusion process they use stable, naturally plentiful spherical nuclei and medium-weight projectiles, not, as expected earlier, the heaviest radioactive man-made nuclei and correspondingly light projectiles. Fusion must take place at the lowest possible bombardment energy, and not, as believed earlier, with excess impact energy to assist the process by brute force.

• OSTI ID: 6481060
• Journal Information: Scientific American; (USA), Vol. 260:5; ISSN 0036-8733
• Country of Publication: United States
• Language: English

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SYNTHESIS
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HEAVY ION FUSION REACTIONS
ISOTOPE PRODUCTION
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651000* - Nuclear Physics