Appendix E — Nuclear Databases and Online Resources

Nuclear physics is, among other things, a data-intensive science. The chart of nuclides contains over 3,300 experimentally observed nuclides, each characterized by dozens of properties — masses, half-lives, level schemes, transition rates, cross sections, decay modes, and more. No single experiment measures all of these quantities, and no single publication compiles them. Instead, the nuclear physics community maintains a network of evaluated databases that aggregate, critically assess, and disseminate nuclear data from tens of thousands of original measurements.

This appendix is a practical guide to the databases you will encounter most frequently in this textbook and in nuclear physics research. For each resource, we describe what it contains, how to access it, and how to perform the queries most relevant to the topics covered in Chapters 1 through 35. Where stable URLs exist, we provide them; where interfaces change frequently, we describe the navigation path.

💡 Practical Advice: Bookmark these resources now. You will use them repeatedly throughout this course — for homework, for the capstone project (Chapter 34), and long after you finish this book.

E.1 National Nuclear Data Center (NNDC) at Brookhaven National Laboratory

The NNDC, operated by Brookhaven National Laboratory (BNL) under the auspices of the U.S. Department of Energy, is the single most important portal for nuclear structure and decay data. It hosts several interconnected databases and interactive tools.

URL: https://www.nndc.bnl.gov/

E.1.1 NuDat: Interactive Chart of Nuclides

NuDat is an interactive, web-based interface to nuclear structure and decay data. It presents the chart of nuclides as a color-coded grid where each cell represents a nuclide, color-coded by decay mode (blue for beta-minus, pink/red for beta-plus/EC, yellow for alpha, green for stable, etc.).

What it contains:

  • Ground-state properties: half-life, spin-parity ($J^\pi$), mass excess, binding energy per nucleon, separation energies, quadrupole moments, magnetic moments
  • Decay properties: decay modes, branching ratios, $Q$-values, daughter products
  • Excited states: level schemes with energies, $J^\pi$ assignments, gamma-ray energies and intensities, internal conversion coefficients, multipolarities
  • Radiation information: energies and intensities of emitted alphas, betas, gammas, X-rays, conversion electrons, Auger electrons

How to use it:

  1. Navigate to the NuDat page from the NNDC homepage or directly at https://www.nndc.bnl.gov/nudat3/.
  2. Click on any nuclide in the chart to view its properties. Zoom and pan to navigate.
  3. Use the "Decay Radiation" tab to obtain gamma-ray energies and intensities — essential for identifying nuclides in spectroscopy (Chapters 9, 15, 30).
  4. Use the "Levels and Gammas" tab to view the complete level scheme — the backbone of nuclear structure information (Chapters 6, 7, 8).
  5. Use the search function to look up nuclides by element name, $Z$, $A$, or isotope symbol.

Example query (relevant to Chapter 6): Look up $^{208}$Pb. Note the doubly-magic structure: the first excited state is at 2.615 MeV ($3^-$), far above the ground state, confirming the large shell gap at $Z = 82$, $N = 126$. The level scheme shows a clear vibrational pattern at low excitation energy.

Example query (relevant to Chapter 12): Look up $^{137}$Cs. Note the half-life (30.08 y), the dominant beta-minus decay to $^{137}$Ba, and the 661.7 keV gamma ray (from the $^{137m}$Ba isomer) with 85.1% intensity per decay. This is the signature line used for environmental monitoring of Chernobyl and Fukushima contamination (Chapter 29).

E.1.2 ENSDF: Evaluated Nuclear Structure Data File

ENSDF is the most comprehensive evaluated database of nuclear structure information. Unlike NuDat, which provides a user-friendly graphical interface, ENSDF contains the full evaluated data sets with detailed documentation, uncertainties, and references to the original experimental literature.

What it contains:

  • Complete level schemes for all known nuclides
  • Gamma-ray transition data: energies, intensities, multipolarities, mixing ratios, conversion coefficients
  • Decay data: alpha, beta, gamma, internal conversion, electron capture
  • Reaction data used to establish level schemes
  • Evaluated uncertainties and references to original publications

How to access it:

  • Through the NNDC web interface: search by nuclide at https://www.nndc.bnl.gov/ensdf/
  • Download complete ENSDF data sets in standard format for offline analysis
  • Through the ENSDF retrieval interface, which allows queries by nuclide, mass chain, or adopted levels

How to use it: ENSDF data is organized by mass chain ($A$). For each mass number, there are "adopted levels" datasets (the recommended values) and individual datasets from specific experiments or decay studies. For research-level work, always consult the adopted levels. For understanding how a particular level was established, examine the individual datasets.

Data format: ENSDF uses a fixed-format text encoding (80-character records) that dates to the punch-card era. While archaic, this format is well-documented and parseable with standard scripts. Python libraries such as pyne and nudel can read ENSDF format directly.

E.1.3 ENDF: Evaluated Nuclear Data File

ENDF is the primary U.S. library of evaluated nuclear reaction data, maintained at the NNDC. It is the workhorse database for nuclear reactor design, criticality safety, radiation shielding, and medical physics calculations.

What it contains:

  • Neutron-induced reaction cross sections from thermal to 20 MeV (and higher for some nuclides)
  • Charged-particle reaction cross sections
  • Photonuclear reaction data
  • Thermal neutron scattering law data
  • Fission product yields
  • Radioactive decay data
  • Neutron and charged-particle emission spectra

How to access it:

  • Sigma interface: https://www.nndc.bnl.gov/sigma/ — an interactive plotter for ENDF cross sections. This is the fastest way to plot and compare cross sections.
  • Download ENDF-B/VIII.0 (the current major release) in ENDF-6 format for use with transport codes such as MCNP, Geant4, FLUKA, and OpenMC.

Example query (relevant to Chapter 18): Plot the total neutron cross section of $^{238}$U from 1 eV to 1 MeV using Sigma. Observe the rich resonance structure in the eV–keV region — each resonance corresponds to a compound nucleus state in $^{239}$U, as described by the Breit-Wigner formalism of Chapter 18.

Example query (relevant to Chapter 20): Compare the fission cross sections of $^{235}$U and $^{238}$U. Note that $^{235}$U has a large thermal fission cross section ($\sigma_f \approx 585$ b at 0.0253 eV) while $^{238}$U requires neutrons above approximately 1 MeV to fission — the threshold fission behavior that determines reactor physics (Chapters 20, 26).

E.1.4 XUNDL: Experimental Unevaluated Nuclear Data List

XUNDL is the repository for recently published nuclear structure data that has not yet been incorporated into ENSDF evaluations. If you are looking for the very latest experimental results on a particular nuclide, XUNDL is the place to check. It contains data compiled directly from journal articles, often within months of publication.

URL: https://www.nndc.bnl.gov/xundl/

E.1.5 Wallet Cards

The Nuclear Wallet Cards provide a compact summary of ground-state properties (half-life, $J^\pi$, decay modes, $Q$-values, and natural abundance) for all known nuclides. Available as a downloadable PDF or a searchable web interface.

URL: https://www.nndc.bnl.gov/wallet/

E.2 Atomic Mass Evaluation (AME) and the Atomic Mass Data Center (AMDC)

E.2.1 The Atomic Mass Evaluation

The Atomic Mass Evaluation is a comprehensive, critically evaluated compilation of all experimental atomic mass measurements. Published periodically since 1960, the current edition is AME2020 (published in 2021 by Wang, Huang, Kondev, Naimi, and Audi in Chinese Physics C).

What it contains:

  • Experimentally measured atomic masses for over 2,500 nuclides
  • Extrapolated masses for approximately 900 additional nuclides (based on systematic trends)
  • Mass excess values $\Delta = M - A \cdot u$ in keV
  • Binding energies $B(Z,N)$
  • One-nucleon and two-nucleon separation energies ($S_n$, $S_p$, $S_{2n}$, $S_{2p}$)
  • Reaction $Q$-values
  • Detailed uncertainty budgets

How to access it:

  • The AME2020 tables are available from the AMDC website: https://www-nds.iaea.org/amdc/
  • The data tables are published as supplementary files in Chinese Physics C and are freely downloadable
  • Machine-readable ASCII tables (mass_1.mas20, rct1_1.rct20, etc.) are the standard format for computational use

How to use it:

The most common operation is looking up the mass excess $\Delta(Z,N)$ for a particular nuclide. From the mass excess, you can compute:

  • Binding energy: $B(Z,N) = Z \cdot \Delta_H + N \cdot \Delta_n - \Delta(Z,N)$, where $\Delta_H = 7288.971$ keV and $\Delta_n = 8071.318$ keV are the mass excesses of hydrogen and the neutron
  • $Q$-value for any reaction: $Q = \sum_i \Delta_i(\text{reactants}) - \sum_j \Delta_j(\text{products})$
  • Separation energies: $S_n = B(Z,N) - B(Z,N-1)$

These calculations appear throughout this textbook, beginning with Chapter 1 (binding energy curve), Chapter 4 (SEMF), and Chapter 12 (decay $Q$-values).

Example query (relevant to Chapter 4): Download the AME2020 mass table and extract the binding energy per nucleon $B/A$ for all nuclides with measured masses. Plot $B/A$ versus $A$ to reproduce the binding energy curve from Chapter 1. Overlay the SEMF prediction and identify systematic deviations at magic numbers — the shell effects that the liquid drop model misses.

E.3 TENDL: TALYS-based Evaluated Nuclear Data Library

TENDL is a nuclear data library produced by running the nuclear reaction code TALYS on all target nuclides for neutrons and protons from 1 keV to 200 MeV. It is updated annually or biennially (the current release is TENDL-2023).

What it contains:

  • Complete sets of neutron- and proton-induced reaction cross sections
  • Residual production cross sections (useful for activation calculations)
  • Covariance data (uncertainty quantification)
  • Data for nuclides and reactions that may not appear in ENDF because of insufficient experimental data — TENDL uses nuclear models (TALYS) to fill gaps

How to access it:

  • TENDL website: https://tendl.web.psi.ch/tendl_2023/tendl2023.html
  • Data is available in ENDF-6 format, directly usable in transport codes
  • Interactive plotting tools are available on the website

When to use TENDL vs. ENDF: Use ENDF/B-VIII.0 when high-accuracy evaluated data exists (the major actinides, structural materials, dosimetry nuclides). Use TENDL when you need data for exotic nuclides, proton-induced reactions, or when you need covariance information that ENDF does not provide.

E.4 IAEA Nuclear Data Services

The International Atomic Energy Agency (IAEA) maintains a comprehensive nuclear data portal in Vienna.

URL: https://www-nds.iaea.org/

E.4.1 EXFOR: Experimental Nuclear Reaction Data

EXFOR (also written CSISRS in earlier literature) is the international repository of experimental nuclear reaction data. While ENDF and TENDL contain evaluated data (recommended values derived from multiple experiments), EXFOR contains the raw experimental data points from individual measurements.

What it contains:

  • Over 24,000 experimental datasets from nuclear reaction measurements worldwide
  • Cross sections, angular distributions, energy spectra, fission yields, and resonance parameters
  • Bibliographic information linking each dataset to the original publication

How to access it:

  • IAEA EXFOR web interface: https://www-nds.iaea.org/exfor/
  • Search by reaction (e.g., 27-Co-59(n,gamma)27-Co-60), by author, by reference, or by energy range
  • Results can be plotted interactively or downloaded in tabular format

How to use it: EXFOR is invaluable when you want to see the spread of experimental data, understand disagreements between measurements, or trace a cross section value to its original measurement. When teaching Chapter 17 (reaction fundamentals) or Chapter 18 (compound nucleus), plotting EXFOR data alongside ENDF evaluations illustrates how evaluators weight conflicting measurements.

E.4.2 Medical Isotope Browser

The IAEA Medical Isotope Browser provides nuclear data specifically curated for nuclear medicine applications: production cross sections, decay data, and dosimetric quantities for medically relevant radionuclides.

URL: https://www-nds.iaea.org/relnsd/vcharthtml/MEDVChart.html

Relevance: Chapter 27 (nuclear medicine) and Chapter 30 (accelerators) discuss the production and properties of medical isotopes. The Medical Isotope Browser provides recommended cross sections for cyclotron production routes such as $^{18}$O(p,n)$^{18}$F and $^{nat}$Mo(p,x)$^{99m}$Tc.

E.4.3 Other IAEA Resources

  • Nuclear Data for Safeguards: Evaluated data specifically for nuclear security applications (Chapter 28)
  • IBANDL (Ion Beam Analysis Nuclear Data Library): Cross sections for ion beam analysis techniques
  • RIPL (Reference Input Parameter Library): Nuclear model parameters (level densities, optical potentials, gamma-ray strength functions) used as inputs to reaction codes like TALYS and EMPIRE

E.5 REACLIB: Thermonuclear Reaction Rate Library

REACLIB is the standard library of thermonuclear reaction rates used in stellar evolution and nucleosynthesis calculations. Maintained at the Joint Institute for Nuclear Astrophysics (JINA), it provides parametric fits to astrophysical reaction rates as functions of temperature.

URL: https://reaclib.jinaweb.org/

What it contains:

  • Thermonuclear reaction rates $N_A \langle \sigma v \rangle$ for thousands of reactions, parametrized as seven-parameter analytic fits:

$$N_A \langle \sigma v \rangle = \exp\left(a_0 + \sum_{i=1}^{5} a_i T_9^{(2i-5)/3} + a_6 \ln T_9 \right)$$

where $T_9$ is the temperature in units of $10^9$ K.

  • Rates for strong, electromagnetic, and weak reactions
  • Forward and reverse rates (related by detailed balance)
  • Weak interaction rates (electron capture, beta decay) with density and temperature dependence

How to use it:

  1. Search for a reaction by specifying reactants and products (e.g., $^{12}$C($\alpha$,$\gamma$)$^{16}$O)
  2. Download the seven-parameter fit coefficients
  3. Evaluate the rate at any temperature using the formula above
  4. Incorporate rates into a reaction network code

Relevance: Chapters 21 (fusion), 22 (stellar nucleosynthesis), 23 (explosive nucleosynthesis), and 24 (BBN) all use thermonuclear reaction rates. The Python code in stellar_burning.py (Chapter 22) and bbn_network.py (Chapter 24) uses REACLIB rates.

E.6 KADoNiS: Karlsruhe Astrophysical Database of Nucleosynthesis in Stars

KADoNiS is a database of experimentally measured and recommended neutron capture cross sections for the astrophysical $s$-process and $p$-process.

URL: https://kadonis.org/

What it contains:

  • Maxwellian-averaged neutron capture cross sections $\langle \sigma \rangle_{kT}$ at $kT = 5$–100 keV (the relevant energy range for the $s$-process in AGB stars)
  • Stellar enhancement factors (corrections for thermally populated excited states)
  • Both experimental values and recommended values with uncertainties
  • Cross sections for $(n,\gamma)$, $(n,p)$, $(n,\alpha)$, and $(\gamma,n)$ reactions relevant to the $p$-process

How to use it:

  • Search by element or nuclide
  • Download recommended Maxwellian-averaged cross sections at standard $s$-process temperatures ($kT = 30$ keV is the canonical thermal energy for the main $s$-process)
  • Use these cross sections to calculate $s$-process abundances: at steady-state flow equilibrium, $\sigma_A N_A \approx \sigma_{A+1} N_{A+1}$, where $\sigma_A$ is the MACS and $N_A$ is the abundance (Chapter 23)

Relevance: Chapter 23 discusses the $s$-process in detail. The local approximation to $s$-process abundances ($\sigma N = \text{const}$) can be tested quantitatively using KADoNiS cross sections.

E.7 NIST Physical Reference Data

The National Institute of Standards and Technology (NIST) maintains several databases relevant to radiation interactions with matter.

URL: https://www.nist.gov/pml/productsservices/physical-reference-data

E.7.1 XCOM: Photon Cross Sections

XCOM provides photon interaction cross sections (photoelectric absorption, Compton scattering, pair production, and total attenuation) for any element, compound, or mixture at energies from 1 keV to 100 GeV.

URL: https://physics.nist.gov/PhysRefData/Xcom/html/xcom1.html

How to use it: Enter the target material (by element, compound formula, or custom mixture), specify the energy range and grid, and obtain tabulated cross sections. These data are essential for radiation shielding calculations (Chapter 16, Appendix F) and medical physics dose calculations (Chapter 27).

Example query (relevant to Chapter 16): Obtain the total mass attenuation coefficient $\mu/\rho$ for lead at photon energies from 10 keV to 10 MeV. Identify the photoelectric, Compton, and pair production contributions. Note the K-edge at 88 keV and the crossover from Compton dominance to pair production at approximately 5 MeV.

E.7.2 PSTAR and ASTAR: Stopping Powers for Protons and Alpha Particles

PSTAR provides stopping powers and ranges for protons in any elemental material; ASTAR does the same for alpha particles. These are based on the Bethe-Bloch theory with empirical corrections.

URL: https://physics.nist.gov/PhysRefData/Star/Text/intro.html

How to use it: Select the target material and energy range. The output includes electronic stopping power, nuclear stopping power, total stopping power, CSDA range, projected range, and detour factor.

Relevance: Chapter 16 (radiation interactions) derives the Bethe-Bloch formula; PSTAR/ASTAR data can validate those derivations. Chapter 27 (nuclear medicine) uses proton stopping powers to compute Bragg peak positions for proton therapy planning.

E.7.3 ESTAR: Stopping Powers for Electrons

ESTAR provides the analogous data for electrons and positrons. Useful for beta-decay dosimetry calculations (Chapter 14, Chapter 27).

URL: https://physics.nist.gov/PhysRefData/Star/Text/ESTAR.html

E.8 Additional Resources

E.8.1 Brookhaven Linac Isotope Producer (BLIP) and IAEA Isotope Production Data

For cross sections of isotope production reactions relevant to medical and industrial isotopes, the IAEA maintains recommended excitation functions at https://www-nds.iaea.org/medical/.

E.8.2 OECD/NEA Data Bank

The OECD Nuclear Energy Agency maintains a parallel nuclear data portal (Paris) that mirrors many ENDF/JEFF/JENDL libraries and provides additional benchmarking databases for reactor physics validation.

URL: https://www.oecd-nea.org/jcms/pl_39910/janis

JANIS (Java-based Nuclear Data Information System) is their interactive cross section plotter, functionally similar to NNDC Sigma but with additional access to the European JEFF and Japanese JENDL libraries.

E.8.3 T2 Nuclear Information Service (LANL)

Los Alamos National Laboratory's T-2 group maintains nuclear data resources at https://t2.lanl.gov/, including ENDF data access, Hauser-Feshbach calculations, and fission product yield data.

E.8.4 nubase2020 and NUBASE Evaluated Nuclear Properties

Published alongside AME2020, NUBASE2020 provides recommended values of nuclear and decay properties (half-lives, $J^\pi$, decay modes, branching ratios) for all known nuclear ground states and isomers. Available from the AMDC website.

E.9 Tips for Working with Nuclear Data

  1. Start with NuDat for quick lookups. If you need the half-life, $J^\pi$, or dominant decay mode of a nuclide, NuDat is the fastest path.

  2. Use ENSDF for research-quality data. If you need complete level schemes with uncertainties, multipolarities, and mixing ratios — or if you need to trace a value to its original measurement — use ENSDF.

  3. Use ENDF/Sigma for cross sections. For neutron cross sections relevant to reactors, shielding, or activation, start with the Sigma plotter. For astrophysical reactions, go to REACLIB or KADoNiS.

  4. Always check the evaluation date. Nuclear data evaluations are updated periodically. The most recent evaluation may incorporate new measurements that significantly change recommended values — especially for exotic nuclides far from stability.

  5. Cross-check between databases. For critical applications, compare ENDF values with EXFOR experimental data. If the evaluation is old and new measurements exist, the evaluated value may be outdated.

  6. Cite your data sources. Nuclear data have authors. When you use AME masses, ENSDF level schemes, or ENDF cross sections in a publication, cite the relevant evaluation. The standard references are provided on each database's website.

  7. Use Python for bulk access. For systematic studies involving hundreds or thousands of nuclides, download the machine-readable tables and process them with Python (or the pyne library, which provides programmatic access to many nuclear data formats). The Python toolkit in Appendix D includes functions for reading AME and ENSDF data.

📊 Capstone Connection: The capstone project (Chapter 34) requires you to assemble nuclear data from multiple sources for a nuclide or reaction of your choice. This appendix serves as your roadmap. Chapter 35 provides additional guidance on navigating the nuclear physics literature.