ensdf evaluation for a=260-265

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

ENSDF evaluation forA=260-265

M. Gupta Manipal University, Manipal, India

T. W. BurrowsNational Nuclear Data Center,

Brookhaven National Laboratory, USA


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

Motivation for evaluation


Chart of Nuclides showing Chart of Nuclides showing A=260-265 regionA=260-265 region

Cold fusion

Hot fusion

A=265

A=260

Physics interest:

Deformed shell region

N ~162-164


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


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’)


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

τu = Upper limit (estimate); τl = lower limit (estimate)

tm = average mean time; z = 1 for 68% confidence level;

n = # of eventsExpected accuracy of approximation: within 10%


“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:


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. 265/266Sg 261/262Rf

Cross-sections including revisions in cross-sections following re-interpretation

of data (e.g. 262/263Db) Reassignments --- existing data

noted in both original and “re-assigned” data sets SF: TKE, mass distributions, n-multiplicity Chemical properties


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


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

ensdf evaluation for a=260-265

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