Doubly Magic nuclear physics answers fundamental questions about the universe
Friday 22 June 2012
New research involving experts at the University of Surrey into the structure of extremely rare atomic nuclei is providing the deepest insights yet into the formation of heavy elements that occur during explosions on the surface of stars in space.
The research carried out by an international team of scientists at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, represents a major milestone in current nuclear structure physics research, the results of which have been published in Nature, 20th June 2012.
The team of researchers, including nuclear physicists from the Universities of Surrey and Edinburgh, supported by the Science and Technology Facilities Council (STFC), has performed the first experiment to study the radioactive decay of Tin-100.
A very rare and unstable isotope of Tin, Tin-100 does not occur in nature, but only on the surface of exploding stars, and for no more than a second. It is also the heaviest element observed with equal proton and neutron numbers.
To study the isotope in detail the team at GSI used a highly specialised gamma-ray detector, known as RISING, designed and developed by the Nuclear Physics Group at STFC’s Daresbury Laboratory and the University of Liverpool. The most powerful instrument of its kind in the world, the researchers were able to use RISING to measure the half-life and decay energy of Tin-100 and its decay products, as it captured the extremely weak gamma rays emitted as it decayed.
Professor Paddy Regan, of the University of Surrey and spokesperson for the RISING collaboration which undertook the research on Tin-100 worked closely with fellow Surrey physicist Dr Zsolt Podolayk on the project.
Professor Regan said: “Tin-100 is the heaviest of all nuclei with equal proton and neutron numbers that can currently be studied at this level and it’s great to observe such fascinating results. This detailed study of the internal structure of this most exotic nucleus also gives new and unique insights into the internal structure of atomic nuclei and the creation of elements heavier than iron. ”
Not only is Tin-100 extremely rare, it is also 'magic’, according to the ‘shell model of nuclear physics’, which identifies a small handful of ‘magic numbers’, one of which is number 50, that give rise to special properties. Tin-100 is therefore ‘doubly magic’ because it comprises 50 protons and 50 neutrons, and is of particular interest to nuclear physicists as it is the heaviest atomic nucleus, with equal numbers of protons and neutrons yet to be observed.
The Tin-100 nuclei exist on average for only one second before changing to form another element, indium-100. This change arises from the transformation of a single proton in Tin-100 to a neutron via the nuclear process of decay. The research showed that the speed of this decay in Tin-100 is the fastest of its kind so far observed, and presents indisputable evidence for a very simple underlying quantum shell structure for the protons and neutrons to form the Tin-100 nucleus.
Professor Philip Woods, Head of the Nuclear Physics Group at the University of Edinburgh, said: “This result illustrates the fundamental insights into nuclear structure and decay processes that can be gained by the study of these rare doubly-magic nuclei. It also shows the importance of UK nuclear physicists playing leading roles in both the science programme and development of advanced detection systems at world leading laboratories such as GSI."
Professor John Simpson, Head of STFC’s Nuclear Physics Group, said: “Nuclear physicists look to create and study the very heaviest elements predicted to exist. It is really exciting to see technology developed by the Nuclear Physics Group at STFC and UK Universities contribute to this research that could answer some of the most fundamental questions about our universe. Furthermore, the instruments and techniques developed through this kind of research can normally go on to be applied to a wide range of other areas including energy generation and the diagnosis and treatment of cancers.”
This research paves the way for further UK science programmes at the future international FAIR accelerator (Facility for Antiproton and Ion Research) at GSI, where the UK will play a significant role in this growing area of atomic science through a collaboration called NuSTAR (Nuclear Structure Astrophysics and Reactions).
Notes to Editors
Superallowed Gamow-Teller Decay of the Doubly Magic Nucleus Sn-100, Hinke et al., Nature, 21. Juni 2012 – DOI: 10.1038/nature11116
Images available on request: RISING Gamma Ray detector
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