July 27, 2001 

Berkeley Lab Research News

Results of Element 118 Experiment Retracted

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BERKELEY, CA — The team of Berkeley Lab scientists that announced two years ago the observation of what appeared to be Element 118 -- heaviest undiscovered transuranic element at the time -- has retracted its original paper after several confirmation experiments failed to reproduce the results.

A technical committee of experts from the Laboratory’s physics, supercomputing, and nuclear science divisions is reviewing the data and methodology from that 1999 result. Subsequent re-analyses of the original data with different software codes have been unsuccessful in observing atomic decay patterns, or chains, which would confirm the existence of element 118.

In a brief statement submitted to Physical Review Letters, the same publication in which the original results were announced, the research team stated: "In 1999, we reported the synthesis of element 118 in the (lead-krypton) reaction based upon the observation of three decay chains, each consisting of an implanted heavy atom and six sequential high-energy alpha decays, correlated in time and position. Prompted by the absence of similar decay chains in subsequent experiments, we (along with independent experts) re-analyzed the primary data files from our 1999 experiments. Based on these re-analyses, we conclude that the three reported chains are not in the 1999 data. We retract our published claim for the synthesis of element 118."

"Science is self-correcting," Berkeley Lab Director Charles Shank said. "If you get the facts wrong, your experiment is not reproducible. In this case, not only did subsequent experiments fail to reproduce the data, but also a much more thorough analysis of the 1999 data failed to confirm the events. There are many lessons here, and the lab will extract all the value it can from this event."

The original experiment and two confirmation runs were performed at the Laboratory’s 88-inch cyclotron, utilizing a newly installed device called the Berkeley Gas-Filled Separator (BGS). In the experiment, targets of lead were bombarded with an intense beam of high-energy krypton ions. The detected sequence of decay events for elements 118 and 116, if observed, would be consistent with theories that have suggested an "island of stability" for nuclei.

In addition to the confirmation tests at Berkeley, scientists at the GSI laboratory in Germany and the RIKEN lab in Japan were unable to duplicate the original reported results.

Shank said that, in retracting the paper, the experimenters are taking responsibility to clear the record. "The path forward is to learn from the mistakes and to strengthen the resolve to find the answers that nature still hides from us," he added.