Scientists at Lawrence Berkeley National Laboratory (LBL) have formally retracted their claims for the discovery of the most massive chemical element. The synthesis of the "superheavy" element 118, comprising 118 protons and 175 neutrons, was announced in a 1999 paper in Physical Review Letters. The results appeared to confirm theories from the 1970s that predicted heightened stability for nuclei containing around 114 protons and 184 neutrons.

The retraction, published in the current Physical Review Letters, follows failures to reproduce the reported results by the Berkeley researchers and also by scientists in Germany and Japan. After re-analysis of the original data using different software codes, the team was forced to admit that their evidence for element 118 was spurious, prompting all but one of the original papers authors to endorse the retraction.

The initial results had been seen as an early success for the newly constructed Berkeley Gas-filled Separator (BGS). The team bombarded a lead-208 target with neutron-rich krypton-86 ions, in an 88-inch Cyclotron, creating heavy compound nuclei. They then used strong magnetic fields in the BGS to separate the putative element 118 ions. The Berkeley lab is not currently answering questions about how the misidentification process occurred, but some media outlets have reported falsification of the results by one team member.

The original announcement came soon after the successful production of element 114 by scientists at Russias Joint Institute for Nuclear Research in Dubna , in January 1999. LBL researchers believed that their newly formed element 118, dubbed "ununoctium" (meaning one-one-eight), radioactively decayed within milliseconds, to create the element 116--also never previously synthesized. Since then, the Russian scientists have used a different method to reproduce element 116, but at least for now, element 118 must remain crossed off the Periodic Table.