Beginning in the late 1950s, scientists including Gertrude Scharff-Goldhaber at Brookhaven and theorist Wladyslaw Swiatecki, who had recently moved to Berkeley and is a retired member of Berkeley Lab’s NSD, calculated that superheavy elements with certain combinations of protons and neutrons arranged in shells in the nucleus would be relatively stable, eventually reaching an “Island of Stability” where their lifetimes could be measured in minutes or days – or even, some optimists think, in millions of years. Early models suggested that an element with 114 protons and 184 neutrons might be such a stable element. Longtime Berkeley Lab nuclear chemist Glenn Seaborg, then Chairman of the Atomic Energy Commission, encouraged searches for superheavy elements with the necessary “magic numbers” of nucleons.
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.Says Gregorich, “Based on the ideas of the 1960s, we thought when we got to element 114 we would have reached the Island of Stability. More recent theories suggest enhanced stability at other proton numbers, perhaps 120, perhaps 126. The work we’re doing now will help us decide which theories are correct and how we should modify our models.”
Nitsche adds, “During the last 20 years, many relatively stable isotopes have been discovered that lie between the known heavy element isotopes and the Island of Stability – essentially they can be considered as ‘stepping stones’ to this island. The question is, how far does the Island extend – from 114 to perhaps 120 or 126? And how high does it rise out the Sea of Instability.”
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