 A single atom of flerovium , decaying by alpha emission with a lifetime of 30 @.@ 4 seconds , was detected . The decay energy measured was 9 @.@ 71 MeV , giving an expected half @-@ life of 2 – 23 s . This observation was assigned to the isotope flerovium @-@ 289 and was published in January 1999 . The experiment was later repeated , but an isotope with these decay properties was never found again and hence the exact identity of this activity is unknown . It is possible that it was due to the metastable isomer 289mFl . 
