Japanese team claims ‘element 113’ found
First addition to periodic table by Asian researchers
A team of researchers at the Riken Radioisotope Beam Factory within the Riken Nishina Centre for Accelerator-Based Science in Japan claims to have created element 113, the lowest ‘missing link’ on the periodic table. If verified, this will be the first element to have been discovered in Asia and will cap nine years of work under team leader Kosuke Morita.
The new element, provisionally named Ununtrim (Uut) until the discovery is confirmed and the team is given naming rights, is a synthetic metal element with an atomic mass of 284. It does not exist in nature. Like most massive atoms, Uut is inherently unstable, being created and decaying in a fraction of a second.
Morita and his team used a custom-built gas-filled recoil ion separator coupled to a position-sensitive semiconductor detector to identify reaction products. They synthesised the new element by colliding zinc nuclei into a thin layer of bismuth to produce a very heavy ion and observed as this rapidly lost ? particles consisting of two protons and two neutrons each.
Via this cascade, element 113 turned into element 111, 109, 107, 105, 103 and lastly 101, all of which are synthetic too. Observing the decay chain, Morita said, gave “unambiguous proof that element 113 is the origin of the chain”. This had been lacking in experiments the group carried out in 2004 and 2005, leaving them unable to claim the discovery at the time.
These earlier tests had only succeeded in identifying four decay events followed by the spontaneous fission of dubnium-262 (105). As no ? decay of this isotope could be observed at the time, naming rights were no granted because the final products were not then well-known nuclides. However, the chain that was detected this time took the alternative ? route, following well-known paths.
Of the 20 super-heavy elements that have been progressively synthesised since 1940, numbers 93 to 103 were discovered in the US, 104 to 106 and 114 to 116 in the US and Russia and 107 to 112 in Germany. Ununoctium, or element 118 is the most massive yet identified. "For our next challenge, we look to the uncharted territory of element 119 and beyond,” Morita said.