Japanese Scientists in Quest for Element 113

Physicists at the RIKEN Nishina Center for Accelerator-based Science, Japan, have obtained the most unambiguous data to date on the elusive 113th atomic element.

For many years, a team led by Dr Kosuke Morita has conducted experiments at the RIKEN Linear Accelerator Facility in search for the 113th element, using a custom-built gas-filled recoil ion separator coupled to a position-sensitive semiconductor detector to identify reaction products.

On August 12, 2012, the team used zinc ions and 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 the 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). In addition to spontaneous fission, 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 decay chain detected in the latest experiments, however, takes the alternative alpha decay route, with data indicating that dubnium decayed into lawrencium-258 (element 103) and finally into mendelevium-254 (element 101). 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 earlier experimental results, the team’s groundbreaking discovery of the six-step alpha decay chain promises to clinch their claim to naming rights for the 113th element. The results appear in the Journal of Physical Society of Japan.

“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,” Dr 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.”

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Bibliographic information: Kosuke Morita et al. 2012. New Result in the Production and Decay of an Isotope, (278) 113, of the 113th Element. Journal of Physical Society of Japan 81, 103201; doi: 10.1143/JPSJ.81.103201