1. M. Gupta, 20th IAEA-NSDD, Kuwait, 27-31 January, 2013 ENSDF evaluation for A=260-265 M. Gupta Manipal University, Manipal, India T. W. Burrows National Nuclear Data Center, Brookhaven National Laboratory, USA

2. M. Gupta, 20th IAEA-NSDD, Kuwait, 27-31 January, 2013 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 265 Rf : 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 Motivation for evaluation

3. M. Gupta, 20th IAEA-NSDD, Kuwait, 27-31 January, 2013 Chart of Nuclides showing A=260-265 region Cold fusion Hot fusion A=265 A=260 Physics interest: Deformed shell region N ~162-164

4. M. Gupta, 20th IAEA-NSDD, Kuwait, 27-31 January, 2013 Guidelines for evaluation: 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 Priority of discovery for elements in the A=260-265 region already established by IUPAC/IUPAP-TWG/JWP Guidelines serve well to re-visit older data and evaluate new data within a consistent framework

5. M. Gupta, 20th IAEA-NSDD, Kuwait, 27-31 January, 2013 Data checked for: Measurement of excitation functions Cross-bombardments: changing the relative yields of xn-evaporation channels by varying mass number of Projectile or Target (useful in “hot fusion”) Independent verification by another laboratory Redundancy and internal consistency of data Estimates of randomness Consistency of assignments of daughters: secured connection to known descendents; (“cold-fusion”) presence of elemental signatures such as x-rays (in the absence of mass measurements); direct measurements of nuclei in the decay chain by independent chemical studies  determination of Z T1/2 : larger statistics, better value (results can be ‘combined’)

6. M. Gupta, 20th IAEA-NSDD, Kuwait, 27-31 January, 2013 Statistical determination of uncertainties Where not quoted or for combining /including new data Method of K.-H. Schmidt et. al., Z. Phys. A316, 19, 1984 τ u = Upper limit (estimate); τ l = lower limit (estimate) t m = average mean time; z = 1 for 68% confidence level; n = # of events Expected accuracy of approximation: within 10%

7. M. Gupta, 20th IAEA-NSDD, Kuwait, 27-31 January, 2013 “Viola-Seaborg” Phenomenology V. E. Viola and G. T. Seaborg, J. Inorg. Nucl. Chem., v28, p741, 1966 ‘Dubna’ parameter set, obtained by a fit to 65 even-even nuclei:

8. M. Gupta, 20th IAEA-NSDD, Kuwait, 27-31 January, 2013 A=260-265 Available data for 31 observed nuclides considered  A = 265 (4); 264 (3); 263 (6); 262 (5); 261 (6); 260 (7) Experimental details include:  Differences in interpretation of observations for parents and daughters e.g. 265/266 Sg  261/262 Rf  Cross-sections including revisions in cross-sections following re-interpretation of data (e.g. 262/263 Db)  Reassignments --- existing data noted in both original and “re-assigned” data sets  SF: TKE, mass distributions, n-multiplicity  Chemical properties

9. M. Gupta, 20th IAEA-NSDD, Kuwait, 27-31 January, 2013 Chemical studies: A=260-265 region ~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

10. M. Gupta, 20th IAEA-NSDD, Kuwait, 27-31 January, 2013 Conclusions 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