| Nuclide | Energy, keV | Yield, % | Half-life |
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Enter a gamma peak energy in keV (e.g. 661.7 for Cs-137 or 1332.5 for Co-60) and a ± tolerance — the tool finds radionuclides with a gamma line in that energy window, sorts them by yield and shows the half-life. This helps identify a nuclide from a gamma-spectrometer spectrum. Click a nuclide to open its card with all lines.
Gamma lines are taken from the ENDF/B-VIII.0 (NNDC) library for the bare nuclide without daughter ingrowth. Yield is photons per 100 decays. For complex spectra, account for daughters and background.
Ba-137m, the daughter of Cs-137 in secular equilibrium; the search flags it and links to the parent. The 1173/1332 keV pair is Co-60, 59.5 keV is Am-241, 140.5 keV is Tc-99m and 1460.8 keV is natural K-40.
For a NaI(Tl) scintillator 2–3 % of the energy (10–20 keV at 662 keV), for an HPGe detector 1–2 keV. A narrower window gives a shorter list, but with a poor energy calibration the right nuclide may drop out.
They appear in real spectra too: characteristic K and L X-rays (for Am-241 the 59.5 keV line sits next to Np L lines) and 511 keV from positron emitters. The line type is shown so that it is not mistaken for a gamma transition.