Nuclear Structure Data

Introduction

What is structure data ?

Nuclear stucture data refer to the properties of single nuclei, as opposed to reaction data which deals with the properties of a nucleus interacting with radiation or another nucleus.

Numerical data related to nuclear structure are available in the ENSDF and NUDAT databases, and bibliographic information on nuclear structure is found in the NSR database.

The Nuclear Structure and Decay Data Network

The International Nuclear Structure and Decay Data (NSDD) Network is organised under the auspices of the International Atomic Energy Agency, and co-ordinated by the National Nuclear Data Center (NNDC) at the Brookhaven National Laboratory, US. The NSDD Network is responsible for the evaluation of all the mass-chains on a continual basis. A mass-chain is formed by all the nuclides of the same mass and different chemical elements. Each of the members of the network has a permanent assignment of mass-chains depending on the number of evaluators, their research interests, or special expertise in a particular mass region. Evaluations produced by the NSDD Network are stored in the Evaluated Nuclear Structure Data File (ENSDF) database. Links to data centres in the NSDD Network is available from NNDC

The ENSDF database

Contents of the ENSDF database

ENSDF contains evaluated experimental data summarizing the present knowledge on the structure and decay of nuclei. It contains information on nuclear level properties, radiations, radioactive decay, and reaction data for all known nuclides. For masses A ≥ 45, this information is documented in the Nuclear Data Sheets; for A < 45 ENSDF is based on compilations published in the journal Nuclear Physics.

If there are gaps in experimental data, they are not filled with theoretical or nuclear model calculations. While the emphasis is on experimental data, the evaluations do use well-founded systematics or theory.

General Organisation of the ENSDF data

The Evaluated Nuclear Structure Data File is made up of a collection of "data sets" which present one of the following kinds of information:

  1. The evaluated results of a single experiment. e.g., a radioactive decay or a nuclear reaction.
  2. The combined evaluated results of a number of experiments of the same kind. e.g., (Heavy ion, xn gamma), Coulomb excitation, etc.
  3. The adopted properties of the nucleus.
  4. The references used in all the data sets for the given mass number. This data set is based upon reference codes (key numbers) used in various data sets for a given mass number and is added to the file by NNDC.
  5. The summary information for a mass chain giving information, e.g., evaluator's name and affiliation, cutoff date, Nuclear Data Sheets publication details, etc.

The data sets in ENSDF are organised by their mass number. Within a mass number the data sets are of two kinds:

  1. Data sets which contain information pertaining to the complete mass chain. These data sets contain information of the type (4) and (5) given above.
  2. Data sets belonging to a given nucleus (Z-value).

Data sets (ii) i.e., for a given nucleus (Z-value), consist of the following:

  1. Adopted data sets (only one per Z-value) giving adopted properties of the levels and radiations seen in that nucleus.
  2. Data sets giving information of the type (1) or (2) above.

If the is more than one data set of type (1) or (2) for a given nucleus, then an adopted data set is required for that nucleus. If there is only one data set for a given nucleus, then that set is assumed also to present the adopted properties for that nucleus.

ENSDF format manual

A full and detailed description of the ENSDF format is provided in:

"Evaluated Nuclear Structure Data File - A Manual for Preparation of Data Sets", J.K.Tulli, Feb 2001, BNL-NCS-51655-01/02-Rev
Search ENSDF database

This mode of access provides an easy way to make simple searches of the ENSDF database. Simply enter a mass number (1 through 266) or a nuclide in the form ZZAAA (e.g.,235U) or ZZ-AAA (e.g., U-235).

ENSDF analysis and checking programs

A number of analysis and utility codes for use with ENSDF data are available from NNDC. Instructions on retrieving the codes from NNDC are described in "ENSDF Analysis and Checking Codes" (Postscript) or "ENSDF Analysis and Checking Codes"

The NUDAT Database

Contents of the NUDAT database

The NUDAT database contains data extracted from several databases maintained at the National Nuclear Data Center (NNDC). The table below lists the type of data contained in NUDAT, and their origin:

Adopted levels - Adopted nuclear level information from ENSDF
Adopted gammas - Adopted gamma rays from levels in ENSDF
Adopted levels and gammas - Levels and gamma ray information combined
Ground and Metastable state properties - Properties of ground/metastable states from the Wallet Cards
Decay Radiations - ENSDF decay radiations from decay data processed by the code RADLST
Thermal Neutron Data and Resonance Integrals - Thermal neutron cross sections and resonance integrals from BNL325
Search NUDAT database

This mode of access provides an easy way to make simple searches of the NUDAT database. The opening screen invites the user to select the type of data desired (selected from the list of data types shown above). For all data types the chemical symbol (or atomic number) and mass number are offered as search parameters. The other search parameters available are dependent on the data type. A full desciption of possible search criteria, together with examples, can be found on the web page "The NuDat2 Description".

Audi/Wapstra Mass Evaluations

General Information

The AME2003 atomic mass evaluation" is presented here in the form of four files:

The format of these data files are described in each of their headers (first 39 records). Note that the format is not identical to the 1993 and 1995 files.

References:

See also the web page http://www.nndc.bnl.gov/amdc/.

1995 Atomic Mass Evaluation

The table of masses and the table of nuclear reaction and separation energies resulting from the evaluation published in:

"The 1995 Update to the Atomic Mass Evaluation" (Ame'95), G. Audi and A.H. Wapstra, Nuclear Physics A595 (1995) P409-480

are made available in electronic format.

Most readers can best use the set of recommended tables (labelled with `rmd') whereas the more specialized user could with benefit analyze the second set (with label `exp').

The first file, mass_rmd.mas95, contains the table of masses as printed in the reference above, plus the binding energies, the beta-decay energies and the atomic masses.

The next two files correspond to the table of reaction and separation energies (cf. "The 1993 Atomic Mass Evaluation", part II) in two parts of 6 entries each:

rct1_rmd.mas95 for S2n, S2p, Q(a), Q(2B), Q(ep), Q(B-n)
rct2_rmd.mas95 for Sn, Sp, Q(4B), Q(d,a), Q(p,a), Q(n,a)

The last three files with names mass_exp.mas95, rct1_exp.mas95 and rct2_exp.mas95 are identical to the first three files except for the values resulting from the use of the few deviating experimental data, listed in Table~B of Ame'93 and updated in Table~IV-a of Ame'95.

Values in these files are exact (unrounded) copy of the published ones.

mass_rmd.mas95 Recommended masses
rct1_rmd.mas95 Recommended reaction energies, table 1
rct2_rmd.mas95 Recommended reaction energies, table 2
mass_exp.mas95 Experimental masses
rct1_exp.mas95 Experimental reaction energies, table 1
rct2_exp.mas95 Experimental reaction energies, table 2

Last reviewed: 23 September 2010