EVIDENCE FOR THE POSSIBLE EXISTENCE OF A LONG-LIVED SUPERHEAVY NUCLEUS WITH ATOMIC MASS NUMBER A = 292 AND ATOMIC NUMBER Z ≅ 122 IN NATURAL <font>Th</font>

Abstract

Evidence for the possible existence of a superheavy nucleus with atomic mass number A = 292 and abundance of about 1×10 -12 relative to 232 Th has been found in a study of natural Th using inductively coupled plasma-sector field mass spectrometry. The measured mass is different from any species with molecular mass of 292, but it matches the predictions for the mass of an isotope with atomic number Z = 122 or a nearby element. Its deduced half-life of t 1/2 ≥ 10 8 y suggests that a long-lived isomeric state exists in this isotope. The possibility that it might belong to a new class of long-lived high spin super- and hyperdeformed isomeric states is discussed.