The most unambiguous data to date on the elusive 113th atomic element has been obtained by researchers at the RIKEN Nishina Center for Accelerator-based Science (RNC). A chain of six consecutive alpha decays, produced in experiments at the RIKEN Radioisotope Beam Factory (RIBF), conclusively identifies the element through connections to well-known daughter nuclides. The groundbreaking result sets the stage for Japan to claim naming rights for the element.

The search for superheavy elements, which do not occur naturally and must be produced through experiments, is a painstaking process. Since the first was discovered in 1940, countries have competed to synthesize more such elements. The Americans discovered elements 93 to 103, the Russians and Americans discovered elements 104 to 106, the Germans discovered elements 107 to 112, and the Russians and Americans together discovered elements 114 and 116.

Researcher Kosuke Morita and his team at the RNC are now set to make Japan the first Asian country to name an atomic element. For years Morita has searched for the element using a custom-built gas-filled recoil ion separator (GARIS) coupled to a position-sensitive semiconductor detector to identify reaction products. On August 12, his experiments bore fruit: zinc ions collided with a thin bismuth layer to produce a very heavy ion followed by a chain of six consecutive alpha decays identified as products of an isotope of the 113th element.

While Morita's team also detected element 113 in experiments conducted in 2004 and 2005, earlier results identified only four decay events followed by the spontaneous fission of dubnium-262 (element 105). The isotope dubnium-262 is known to also decay via alpha decay, but this was not observed, and naming rights were not granted since the final products were not well known nuclides at the time. The chain detected this time takes the alternative alpha route, with data indicating that dubnium decayed into lawrencium and finally into mendelevium. The decay of dubnium-262 to lawrencium-258 is well known and provides unambiguous proof that element 113 is the origin of the chain.

Combined with their earlier results, the team's groundbreaking discovery promises to clinch their claim to naming rights for the element. "For 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, who persevered believing that one day, 113 would be ours. Next we look to element 119 and beyond."

Reference:

Kosuke Morita et al. "New Result in the Production and Decay of an Isotope, (278)113, of the 113th Element." Journal of Physical Society of Japan, 2012.

DOI: 10.1143/JPSJ.81.103201

URL: http://jpsj.ipap.jp/link?JPSJ/81/103201/