Decay properties of neutron-deficient isotopes (256,257)Db, (255)Rf, Lr-252,Lr-253

Citation
Fp. Hessberger et al., Decay properties of neutron-deficient isotopes (256,257)Db, (255)Rf, Lr-252,Lr-253, EUR PHY J A, 12(1), 2001, pp. 57-67
Citations number
21
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physics
Journal title
EUROPEAN PHYSICAL JOURNAL A
ISSN journal
1434-6001 → ACNP
Volume
12
Issue
1
Year of publication
2001
Pages
57 - 67
Database
ISI
SICI code
1434-6001(200109)12:1<57:DPONI(>2.0.ZU;2-C
Abstract
Isotopes of dubnium (element 105) with mass numbers A = 256, 257, and 258 w ere produced by the reaction Bi-209 (Ti-50,xn)(259-x) Db (x = 1, 2, 3) at p rojectile energies of (4.59 5.08) AMeV. Excitation functions were measured for the 1n, 2n and 3n evaporation channels. The same position of the excita tion function was observed for the 1n channel as for the previously measure d 1n channel of the reaction Pb-208 (Ti-50,1n)(257)Rf. The measured alpha - decay data of (257)Db and its daughter products resulted in the identificat ion of alpha -decaying isomeric states in (257)Db and Lr-253. Two new isoto pes, (256)Db and Lr-252, were produced at the highest bombarding energies o f 4.97 AMeV and 5.08 AMeV. They were identified by delayed alpha-alpha coin cidences. The measured half-lives are (1.6(-0.3)(+0.5)) s for (256)Db and ( 0.36(-0.07)(+0.11)) s for Lr-252. Besides alpha -decay, a spontaneous fissi on activity of T-1/2 = (2.3(-0.6)(+1.1)) s was observed and attributed to a n electron-capture branch of (256)Db, which feeds the fissioning nucleus (2 56)Rf. A branching ratio of 0.36 +/- 0.12 was obtained. The isotope (255)Rf was produced by the reaction Pb-207 (Ti-50,2n)(255)Rf. Improved decay data have been obtained by means of alpha- and alpha-gamma spectroscopy.