EXISTENCE OF LONG-LIVED ISOTOPES OF A SUPERHEAVY ELEMENT IN NATURAL Au

Evidence for the existence of long-lived isotopes with atomic mass numbers 261 and 265, and abundance of (1 - 10) x 10(-10) relative to Au, has been found in a study of natural Au using inductively coupled plasma-sector field mass spectrometry. The measured masses match the predictions for the masses of (261)Rg and (265)Rg (Z = 111), and those of some isobars of nearby elements. Based on chemical arguments, it is proposed that they are most probably isotopes of Rg. It is deduced that long-lived isomeric states exist in these isotopes. The hypothesis that they belong to a new class of long-lived high spin super- and hyperdeformed isomeric states is discussed.