88 Ra 226 (Z=88, N=138)

The nuclide Ra 226 is an isotope of the element radium (atomic number 88, chemical symbol Ra). There are 226 nucleons in the nucleus consisting of 88 protons and 138 neutrons. Ra 226 is radioactive with a half-life of 1600 years.



Ra 226: Extract from the

Karlsruhe Nuclide Chart, 9th Edition (2015)

            Ra 226: Reduced Decay Scheme


  Main Radiations  





    4.7843 MeV



    4.601 MeV



    186 keV



The colour yellow indicates that the nucleus decays through alpha emission. The alpha particle energy with the highest emission probability is at 4.7843 MeV followed by 4.601 MeV. Additional alpha particles are also observed – indicated by the dots. In contrast to beta emission (where only two beta energies are given – the most probable and the highest energy respectively), the alpha particle energies are listed according to decreasing emission probability.

At the top right hand corner of the box, the violet triangle indicates that Ra 226 undergoes decay by cluster emission. This is a rare type of decay with a very small branching ratio (2.6·10–11). In this particular case the decay is due to C 14 cluster emission. Further details are shown in the decay scheme.

At the bottom of the nuclide box, it can be seen that the cross section for thermal neutron capture to Ra 227 is 12.8 barns. The cross section for fission is very small < 5•10–5 barns.



Half-life: 1600(7) a, V. Chisté et al., Int. Conf. on Nuclear Data for Science and Technology 2007


 α 4.78434(25) MeV, 94.038(40) %

   4.601(1)    MeV,  5.950(40) %


 γ 186.211(13) keV, 3.555(19) %


 V. Chisté et al., Laboratoire National Henri Becquerel, recommended data 2007

 C 14 3.2(16)E-9 %, Nucl.Data Sheets 77(1996)433

 σ: σ 12.8(15) b, σ(f) <5E-5 b, S. Mughabghab, Atlas of Neutron Resonances,

    Resonance Parameters and Thermal Cross Sections Z=1-100, 5th Edition,

    Elsevier, Amsterdam (2006)