Nuclear physics: the quest for the unknown element

Photo: Gaby Otto / GSI

A handful of atoms, synthetically generated, which exist for milliseconds and then disintegrate again immediately – research scientists who want to seek out new elements have to put in a great deal of effort for this fleeting moment. How do synthetic elements originate and why are they being sought out?

In order to find new elements, research scientists make existing atoms collide with high energy. This can cause elements to exist for a short time which have never been visible before. There can also be heavy elements with a high number of protons in the atom which are unstable and disintegrate again because of the mutually repellent effect of the positively charged protons. A team headed up by Dirk Rudolph of Lund University (Sweden) blasted calcium ions (20 protons) onto a film with americium (95 protons) at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt. They could then prove traces of the decay of the element with atomic number 115 and its daughter products - including element 113 - which must have existed for a few milliseconds.

"Although evidence of both elements has been reported in accelerator experiments at the Russian nuclear research centre in Dubna, the existence of elements 113 and 115 is yet to be officially recognised by international bodies", said Rudolph. "This is because the research conducted to date has not been able to furnish any direct evidence of the atomic number of the elements observed", said Christoph Düllmann, who heads up research groups which are working on the superheavy elements at the GSI and at the Helmholtz Institute in Mainz. In its latest experiment the team has managed to detect a kind of fingerprint of element 115, identifying photons with energy corresponding to the theoretical expectations on the decay of element 115.

The discovery sent great waves through the media. The New Yorker was one of the publications to feature a relatively long article on the subject of ununpentium - as element 115 has been named (Ununpentium, the Newest Element). Like the discovery of a new planet, the discovery of a new element has no direct effect on our lives to begin with. "This is pure research", said Rudolph, "although the question as to how the results can be directly applied is not being asked at the moment". It is the famous and, in this case, not just the proverbial question as to what holds the world together at its very core. There are many examples in science, however, which illustrate that pure research can lead to totally unforeseen technical applications. "The best example is the World Wide Web", said Rudolph, "which was originally developed at CERN to improve the exchange of data and research results, and now we cannot imagine life without it".

Naturally, experimental nuclear physics is also about testing the assumptions of theoretical nuclear physics. In turn, the results of the experiments flow back into the theory. An "island of stability" is a theoretical possibility. The more positively charged protons there are packed tightly together in an atom nucleus, the more unstable it normally becomes. Nevertheless, it is possible for certain very heavy atom nuclei to regain a more stable state, i.e. a constellation in the atom nucleus which does not allow the element to decay again immediately. These elements might then be able to exist for minutes or even for much longer. A period of this length would mean that a practical application would no longer appear entirely implausible. GSI press release FAQs on element 115 (Lund University)

30.09.2013 , Martin Trinkaus
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