Α-decay mass chains from some heavier nuclei (A≥266) end in this region

α-decay mass chains from some heavier nuclei (A≥266) end in this region

• α-decay mass chains from some heavier nuclei (A≥266) end in this region

• update of this region is due

• Earlier evaluations of these nuclides in : 1999Ar21, 1999Ak02 and 2001Ak11
• 265Rf : 2000Fi12

• the same evaluation methodology adopted for (distant) ancestors could be usefully extended to descendents within an α-decay chain for consistency and uniformity of treatment

• New results / chemistry

As established in 2005Gu33:

• As established in 2005Gu33:

• International Union of Pure and Applied Chemistry, Trans-fermium Working Group (IUPAC-TWG-JWP):

• R. C. Barber et. al., Prog. Part. Nucl. Phys., v29, p453-530, 1992

• IUPAC/IUPAP - TWG is concerned with the discovery of a new element

• ENSDF evaluations seek primarily to adopt the best set of data for a given isotope

Where not quoted or for combining /including new data

• Where not quoted or for combining /including new data

• Method of K.-H. Schmidt et. al., Z. Phys. A316, 19, 1984

~40% nuclides studied using chemistry

• ~40% nuclides studied using chemistry

• Reporting of experimental uncertainties in chemical studies varies with:

• Specific chemical techniques used (e.g. parent half-life not measured in some cases)
• Motivation for experiment (e.g. measurement for presence or absence of nuclide rather than accurate half-life)
• Interpretation of half-lives (e.g. upper or lower limits?)

• Properties derived from chemical studies supported if same nuclides are also studied by “physical” techniques

• Re-assignments possible due to ambiguities in data

Uniform criteria used to evaluate A=260 – 294 region

• Uniform criteria used to evaluate A=260 – 294 region

• Evaluation methodology is internally consistent

• Re-visiting ‘old’ data yields useful information

• Reveals important experimental parameters vital to adopting the best data set in the absence of mass measurements

• e.g. cross-sections / excitation function measurements

• Atomic properties revealed by chemistry

• Chemical methods:

• Increased statistics
• Independent verification