Search for superheavy elements in monazites using chemical enrichment

Abstract

Evidence for the existence of superheavy elements in monazite inclusions embedded in Madagascan mica and surrounded by giant radioactive haloes was given by Gentry et al.¹ who observed photons with energies corresponding to predicted L_α1 X-ray energies of element 126 (at 27.25 keV) and also of elements 116, 124 and 127 in irradiations of such crystals with collimated proton beams. For an unambiguous identification, the detection of further members of the L X-ray series would be most important. In X-ray spectra of monazite samples these transitions are buried under the strong K X-ray peaks of the lanthanide elements. They should, however, become visible after chemical enrichment of the superheavy elements². Such a treatment would also solve background problems due to a γ ray at 27.2 keV from the ¹⁴⁰Ce(p, n)¹⁴⁰Pr nuclear reaction^3–6 and to K X rays of ordinary trace elements⁷. Although our search remained negative we wish to report the results because our approach differs from that followed by others^3,8–14 in experiments which also remained negative or did not provide compelling evidence^6,15.