Synthesis of nuclei of the superheavy element 114 in reactions induced by Ca-48

Citation
Yt. Oganessian et al., Synthesis of nuclei of the superheavy element 114 in reactions induced by Ca-48, NATURE, 400(6741), 1999, pp. 242-245
Citations number
21
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Multidisciplinary,Multidisciplinary,Multidisciplinary
Journal title
NATURE
ISSN journal
0028-0836 → ACNP
Volume
400
Issue
6741
Year of publication
1999
Pages
242 - 245
Database
ISI
SICI code
0028-0836(19990715)400:6741<242:SONOTS>2.0.ZU;2-K
Abstract
The stability of heavy nuclides, which tend to decay by cy-emission and spo ntaneous fission, is determined by the structural properties of nuclear mat ter. Nuclear binding energies and lifetimes increase markedly in the vicini ty of closed shells of neutrons or protons (nucleons), corresponding to 'ma gic' numbers of nucleons; these give rise to the most stable (spherical) nu clear shapes in the ground state. For example, with a proton number of Z = 82 and a neutron number of N = 126, the nucleus Pb-208 is 'doubly-magic' an d also exceptionally stable, The next closed neutron shell is expected at N = 184, leading to the prediction of an 'island of stability' of superheavy nuclei, for a broad range of isotopes with Z = 104 to 120 (refs 1, 2), The heaviest known nuclei have lifetimes of less than a millisecond, but nucle i near the top of the island of stability are predicted to exist for many y ears. (In contrast, nuclear matter consisting of about 300 nucleons with no shell structure would undergo fission within about 10(-20) seconds.) Calcu lations(3-5) indicate that nuclei with N > 168 should already benefit from the stabilizing influence of the closed shell at N = 184. Here we report th e synthesis of an isotope containing 114 protons and 173 neutrons, through fusion of intense beams of Ca-48 ions with Pu-242 targets. The isotope deca ys by or-emission with a half-life of about five seconds, providing experim ental confirmation of the island of stability.