1. The search engine
---------------------

**Data** are stored in a SQLite database, and normally users do not need direct access to it, and do not use SQL language to retrieve the data.

Description and schema of the database are presented `here <./schema/index.html>`_

.. _database-label:

2. Underlying databases
-----------------------

**The main** source is the `ENSDF <https://www.nndc.bnl.gov/ensdf/>`_ database (Evaluated Nuclear Structure Data Files), it is the only database that covers the entire chart of nuclides. 
It is produced by the International Network of Nuclear Structure and Decay Data Evaluators (`NSDD <https://nds.iaea.org/nsdd/history.html>`_), under the auspices of the `IAEA <https://nds.iaea.org>`_

The National Nuclear Data Center at Brookhaven National Laboratory (`NNDC <https://www.nndc.bnl.gov/ensdf/about.jsp>`_) is responsible for coordinating the evaluation effort and for hosting the database.

NDLab database incorporates the ENSDF-derived `RIPL - Discrete Levels segment <https://www-nds.iaea.org/RIPL-3/levels/>`_ database, to which has been added a complete description 
of levels and gamma transitions

A relevant new feature of the NDLab database is the relational link between levels and gammas in the `ENSDF <https://www.nndc.bnl.gov/ensdf/>`_ decay datasets and their 
counterpart in the adopted datasets.

Levels and gamma transitions 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The `RIPL <https://www-nds.iaea.org/RIPL-3/levels/>`_ database is derived from the `ENSDF <https://www.nndc.bnl.gov/ensdf/>`_ database, with contribution 
from `NUBASE <https://www.anl.gov/phy/atomic-mass-data-resources>`_ and `AME <https://www.anl.gov/phy/atomic-mass-data-resources>`_ databases.
NUBASE is used to fix some of the unknown level energies, expressed in the `ENSDF <https://www.nndc.bnl.gov/ensdf/>`_ in terms of "0+X", or "238+X" , etc... where X is an unknown
energy.

`RIPL <https://www-nds.iaea.org/RIPL-3/levels/>`_ also provides, in many cases, a unique value for spin when the `ENSDF <https://www.nndc.bnl.gov/ensdf/>`_  assignment is non-unique or unknown. 
As already said, this is only an additional field that users should take cum grano salis; the original `ENSDF <https://www.nndc.bnl.gov/ensdf/>`_ assignment is 
present in the database and should be used for accurate structure and decay description

The `RIPL <https://www-nds.iaea.org/RIPL-3/levels/>`_ Discrete Levels database is described in:

*  `IAEA Tecdoc 1506 <https://nds.iaea.org/RIPL-3/handbook/ripl2.pdf>`_ Section 3
*  `INDC(NDS)0702, Update of RIPL Nuclear Levels Segment <https://www-nds.iaea.org/publications/indc/indc-nds-0702/>`_
*  `RIPL Levels database <https://www-nds.iaea.org/RIPL-3/levels/>`_
*  `List of "+X" energies assignments <https://www-nds.iaea.org/RIPL/levels/levels-readme.html>`_


Linking Adopted and Decay datasets
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

For a given nuclide, the ENSDF database places the evaluated levels and gamma transitions properties in the "Adopted", which
are derived by making an overall fit of various "Decay" (and "Reaction") datasets.  

It can happen that the same level, or the same gamma, is present in more than one of these datasets with, for example, an energy slightly different
in each occurrence. 

With data scattered in various datasets, and with no easy linking between them, it becames difficult
for users to navigate the data.

Take the following Sm-152 gamma transition as example:

::
    
    Gamma    Start level  End level  Dataset
    energy        energy     energy            

    119.46   1082.842     963.358    Adopted Sm-152

    118.97   1082.816     963.363    Decay   Eu-152   to Sm-152
    119.44   1082.88      963.40     Decay   Eu-152-m to Sm-152
    119.5    1082.77      963.25     Decay   Pm-152   to Sm-152
    ....


The NDlab database links each gamma and each level 
in the "Decay" dataset to the "Adopted" one, removing the multiple, but different, occurrences of a same entity.

.. attention::

    Please note that for accurate structure and decay description, one should revert back to the ENSDF original datasets


3. Data sources
---------------

**When** not otherwise stated, data are from the `ENSDF <https://www.nndc.bnl.gov/ensdf/>`_ database

* **Masses and Q-values**: `AME2020 <https://www.anl.gov/phy/atomic-mass-data-resources>`_, published in `Chinese Phys. C 45, 030002 (2021) and Chinese Phys. C 45, 030003 (2021) <https://doi.org/10.1088/1674-1137/abddb0>`_
* **Abundances**: `NUBASE2020 <https://www.anl.gov/phy/atomic-mass-data-resources>`_ published  in `Chinese Phys. C 45, 030001 (2021). <https://doi.org/10.1088/1674-1137/abddae>`_
* **Fission Yields**: Joint Evaluated Fission and Fusion File (JEFF) 3.1.1
* **Charge Radii**: I.Angeli, K.P. Marinova, *Atomic Data and Nuclear Data Tables* **99** (2013) 69-95 `DOI:10.1016/j.adt.2011.12.006 <http://dx.doi.org/10.1016/j.adt.2011.12.006>`_
* **Atomic radiations** calculated following:  `E.Schönfeld, H.Janßen <https://doi.org/10.1016/S0969-8043(99)00216-X>`_ and its references.
| **Nuclear Moments**: Tables produced by N.J. Stone:
| Table of Recommended Nuclear Magnetic Dipole Moments: Part I - Long-lived States `indc-nds-0794 <https://nds.iaea.org/publications/indc/indc-nds-0794/>`_, 
| Table of Recommended Nuclear Magnetic Dipole Moments - Part II, Short-lived States `indc-nds-0816 <https://nds.iaea.org/publications/indc/indc-nds-0816/>`_, 
| Table of Nuclear Electric Quadrupole Moments `indc-nds-0833 <https://nds.iaea.org/publications/indc/indc-nds-0833/>`_