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ELEMENTS 118 AND 116 RETRACTED
Failures to reproduce experiments lead Berkeley lab to withdraw paper
MITCH JACOBY
Two years after announcing their discovery of two new superheavy elements, researchers at Lawrence Berkeley National Laboratory (LBNL) have retracted their claim. The retraction was posted on July 27 on LBNL's website and will appear in a forthcoming issue of Physical Review Letters.
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RETRACTION Victor Ninov (left) and Gregorich during 1999 experiments at the Berkeley gas-filled separator. |
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LBNL PHOTO |
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In June 1999, LBNL scientists issued a press release claiming that, during nuclear reaction experiments in which a 208Pb target was bombarded with an intense beam of energetic 86Kr ions, they had detected three series of correlated events that signaled creation and subsequent decay of element 118 with 175 neutrons (C&EN, June, 14, 1999, page 6). One of the members of the new element's decay chain was identified as 289116, a second new element. The results were published two months later [Phys. Rev. Lett., 83, 1104 (1999)].
The 208Pb + 86Kr experiment was repeated at LBNL in 2000 and 2001, yet element 118's signature was not observed, says Kenneth E. Gregorich, team leader of Lawrence Berkeley's heavy-element group. Likewise, experiments conducted at heavy-ion research facilities in Germany and Japan failed to confirm the 1999 results.
"We went back to the 1999 data and reexamined the files," Gregorich explains. "The chains of events that we interpreted as originating from element 118 are not in that data set. We just don't understand it, but we felt that it was important to get the word out quickly because there is a lot of theoretical and experimental work being done because of our 1999 publication."
Sigurd Hofmann, a leading nuclear scientist at the Institute for Heavy-Ion Research, Darmstadt, Germany, says "the Berkeley team has behaved very fairly," adding that the retraction "doesn't touch the possibility of synthesizing element 118 in the future. For now, though, the retraction clears the way for further investigation and the possibility of unambiguous discovery."
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