September 27, 2012
Japanese Scientists Claim They Have Concluded Their Search For Element 113
April Flowers for redOrbit.com - Your Universe Online
To date, the atomic element 113 has been elusive, defying attempts to nail down its properties. But now, researchers at the RIKEN Nishina Center for Accelerator-based Science (RNC) claim to have obtained the most unambiguous data available so far.
In experiments at the RIKEN Radioisotope Beam Factory (RIBF), a chain of six alpha decays was produced, conclusively identifying the element through connections to well-known daughter nuclides. The results of this study, published in the Journal of the Physical Society of Japan, have put Japan on the road to claim the rights to name the element.
Searching for super-heavy elements is a difficult and painstaking process, as they do not occur in nature. Rather they are produced through experiments involving nuclear reactors or particle accelerators, via processes of nuclear fusion or neutron absorption. The first such element was discovered in 1940 and the competition to synthesize more has been going on between the United States, German and Russia. U.S. scientists discovered elements 93 to 103, elements 104 to 106 were concurrent U.S. and Russian discoveries, elements 107 to 112 went to the German scientists, and elements 114 and 116 were a collaboration between the U.S. and Russia.
With the latest findings, the Japanese research team is on the fast track to making Japan the first Asian nation to name an atomic element. Associate chief scientist Kosuke Morita and his team have been conducting experiments at the RIKEN Linear Accelerator Facility in Wako, near Tokyo, for many years. They have been searching for the element using a custom-built gas-filled recoil ion separator (GARIS) coupled to a position-sensitive semiconductor to identify reaction products.
This past August, these efforts bore fruit; zinc ions traveling at one-tenth the speed of light collided with a thin bismuth layer to produce a very heavy ion followed by a chain of six consecutive alpha decays. These decays were identified as products of an isotope of the 113th element.
The team has had positive results before, in 2004 and again in 2005 when they detected the element. However, the earlier results identified only four decay events followed by the spontaneous fission of dubnium-262, or element 105. Dubnium-262 is known to decay via alpha decay in addition to spontaneous fission, but this alpha decay was not observed. Naming rights were not granted since the final products were not well known nuclides at the time.
The latest experiments have changed all of that. The decay chain this time took the alternative alpha decay route, with data indicating that dubnium decayed into lawrencium-258 (element 103) and then into mendelevium-254 (element 101). The well-known decay of dubnium-262 to lawrencium-258 provided unambiguous proof that element 113 was the origin of the chain.
These new results, when combined with the earlier experiments, should clinch naming rights for the research team. Currently, element 113 is called by the temporary name of Ununtrium, which means one-one-three.
"For over 9 years, we have been searching for data conclusively identifying element 113, and now that at last we have it, it feels like a great weight has been lifted from our shoulders," Morita said. "I would like to thank all the researchers and staff involved in this momentous result, who persevered with the belief that one day, 113 would be ours. For our next challenge, we look to the uncharted territory of element 119 and beyond."