ORNL Physics Division
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Evaluation of Mass Chains

General Description

The Nuclear Data Program works to support the goals of the US Nuclear Data Program (USNDP) - specifically, to collect, evaluate, and disseminate nuclear physics data for basic nuclear physics and for applied nuclear technology communities in the United States. This work serves to build the foundation of the collective progress of the field of nuclear science, from which is launched the latest experiments, theoretical investigations, and applications. For any particular nucleus or nuclear reaction of interest, there are tens to thousands of relevant studies done over the decades, and the USNDP effort is to gather, critically assess, extend, summarize, and disseminate this information for the community. Researchers can, with a few mouse clicks, reap the benefits of previous work in the field by going to the Evaluated Nuclear Structure Data File (ENSDF) or the Evaluated Nuclear Data File (ENDF) and accessing evaluations that are posted online at the National Nuclear Data Center at BNL.

Detailed Description

The structure properties of nuclei are usually evaluated in groups according to mass, both because of the decays from one nucleus to another in the chain, as well as isospin symmetry. The responsibilities for evaluating all recent work in a mass chain or "A-chain" evaluations have been given out to evaluators at different USNDP Centers; at ORNL we have nuclei from A=241 - 249. Evaluators regularly assess nuclei outside of their primary responsibility to respond to the measurement activity in the field. ORNL has recently evaluated nuclei (or reviewed evaluations of nuclei) with masses 152, 69, 121, 125, and 58.

Technical Description

In our nuclear structure data effort, evaluation of data for nuclei with mass number A = 69 was recently submitted for publication in Nuclear Data Sheets. This work consisted of evaluated nuclear structure data for the 12 nuclides in this mass chain, and is important for nuclear astrophysics: the slow proton capture on 68Se [via levels in 69Br] in X-ray burst nucleosynthesis impedes the creation of heavier elements in these explosions. There are numerous recent studies of the levels of excited states in 69Br and their impact on element creation in X-ray bursts; our evaluation will, for example, enable a new rate for the 68Se proton capture reaction to be determined.


• "Nuclear Data Sheets for A = 69", C.D.Nesaraja, Nucl. Data Sheets (2011) submitted

• "Nuclear Data Sheets for A = 152", M.J. Martin, Nucl. Data Sheets (2011) submitted

• "Nuclear Data Sheets for A = 58", C.D.Nesaraja, S.D.Geraedts, B.Singh, Nucl. Data Sheets 111, 897 (2010)


Caroline Nesaraja, nesarajacd at ornl.gov