Nuclear-decay studies of neutron-rich rare-earth nuclides.

摘要

Neutron-rich rare-earth nuclei were produced in multinucleon transfer reactions of (sup 170)Er and (sup 176)Yb projectiles on (sup nat)W targets at the Lawrence Berkeley Laboratory SuperHILAC and their radioactive decays properties studied at the on-line mass separation facility OASIS. Two unknown isotopes, (sup 169)Dy (t (sub 1/2) (equals) 39 (plus minus) 8 s) and (sup 174)Er(t(sub 1/2) (equals) 3.3 (plus minus) 0.2 m) were discovered and their decay characteristics determined. The decay schemes for two previously identified isotopes, (sup 168)Dy (t(sub 1/2) (equals) 8.8 (plus minus) 0.3 m) and (sup 171)Ho (t(sub 1/2) (equals) 55 (plus minus) 3 s), were characterized. Evidence for a new isomer of 3.0 m (sup 168)Ho(sup g), (sup 168)Ho(sup m) (t(sub 1/2) (equals) 132 (plus minus) 4 s) which decays by isomeric transition (IT) is presented. Beta particle endpoint energies were determined for the decay of (sup 168)Ho(sup g), (sup 169)Dy, (sup 171)Ho, and (sup 174)Er, the resulting Q(beta)-values are: 2.93 (plus minus) 0.03, 3.2 (plus minus) 0.3, 3.2 (plus minus) 0.6, and 1.8 (plus minus) 0.2 MeV, respectively. These values were compared with values calculated using recent atomic mass formulae. Comparisons of various target/ion source geometries used in the OASIS mass separator facility for these multinucleon transfer reactions were performed. 73 refs., 40 figs., 11 tabs.