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4.6 Radioactive elements4.6.1 Table of nuclides‘Table of Isotopes’ by C. M. Lederer and V. S. Shirley (Wiley, 7th ed, 1978) provides a clear and complete compilation of nuclear states and decays, albeit lacking the very latest results. The US National Nuclear Data Center at Brookhaven maintains the Evaluated Nuclear Structure Data File (ENSDF), which contains evaluated information on the nuclides. This is updated periodically, and the contents are published in the journal Nuclear Data Sheets, grouped by mass (for mass numbers below 45 publication is in the journal Nuclear Physics). These must be regarded as the definitive references to the present state of data on the nuclides. In compiling the table below, the condensed data provided by the NUDAT file was generally used (courtesy of the OECD Nuclear Energy Agency). The nuclei listed are those for which information on both mass and half-life exists. Long-lived isomeric states are included and are indicated by the symbol m following the mass number; in some cases energy measurements are insufficiently precise to determine which of the entries for a particular mass number should be considered as the ground state. Fission isomers have not been included. The second column gives the half-life or the natural abundance in atoms per cent; in certain cases both quantities are relevant. It should be noted that the natural isotopic abundance of elements in the Earth’s crust can vary according to the source, particularly in the case of the lighter elements. The third column summarises the decay modes and principal radiations emitted by radioactive nuclides. Branching ratios (where known) are expressed as a percentage of the total decay events and are quoted to the nearest 1%; branches weaker than 0.5% are excluded. The energy of emitted radiations is expressed in MeV. The possible decay modes are β +, β−, β−β− (double beta decay), α, p (proton emission), n (neutron emission), SF (spontaneous fission), EC (electron capture) and IT (isomeric transition—electromagnetic transition from an isomeric state to the ground state of the same nuclide). Generally the dominant decay mode is listed first; however, direct particle emission modes (α, p, n) are always listed first, to distinguish them from emissions following beta decay to particle-unstable daughter states, which are listed after the other decay (thus , β−; 10%n indicates that 10% of the decays consist of β−decay to particle-unstable states which emit neutrons). For β + or β− decay, the energy quoted is the end-point energy; if there is more than one branch then the most energetic branch (stronger than 0.5%) is always listed first, followed, in order of decreasing energy, by the strongest branch (if different) and any other branch stronger than 20%, up to a total of at most three branches. Thus 75% β − (2% 1.5, 35% 1.2, 25% 0.9) indicates that in total 75% of the decays involve β− emission, the highest energy branch has an end-point of 1.5 MeV but a branching ratio of only 2%, the 1.2 and 0.9 MeV branches account respectively for 35% and 25% of the decays, and the remaining 13% is in weaker unlisted branches. It should be noted that in some cases there is a large number of branches closely spaced in energy. For α decay, the four strongest branches are listed in order of energy (thus 55% α (25% 5.55, 10% 5.45, 8% 5.40, 7% 5.38) indicates that 55% of all decays are by α emission, including 50% in the four branches listed and 5% in weaker branches). Cases where some of the decays lead to an isomeric state of the daughter are generally indicated: (88% m) denotes that 88% of all decays lead to an isomeric state. Immediately after the decay modes, the three strongest γ-rays (if any) emitted during the decay of the daughter(s) to their ground state(s) are listed in order of strength. Gamma-rays emitted in the IT decay of a daughter which is itself an isomeric state are generally distinguished by the symbol (m); in such cases if the half-life of the isomeric state is comparable to that of the parent the effective instantaneous branching ratio, listed, is greater than that obtained simply by calculating the probability of a given decay proceeding eventually through this γ-ray. The single entry γ indicates that γ-rays are emitted but the branching ratios are unknown. Annihilation radiation (which always follows β + emission), X-rays, conversion electrons and Auger electrons have not been included. The fourth column gives the mass excess expressed in MeV, i.e. the difference between the measured atomic mass and A atomic mass units on the 12C scale (1 a.m.u. = 931.478 MeV). The fifth column gives the thermal neutron cross-section in barns (10−28 m2) for various processes indicated as follows: (γ) for (n, γ), (γm) for (n, γ) leading to an isomeric state, (p) for (n, p), (α) for (n, α), (f) for neutron-induced fission and (t) for the sum of all absorption processes. The sixth column gives the spin (I) and parity (π).
The Kaye and Laby Table of Nuclides in the 16th edition of the book was over 100 pages long. So as you can imagine it was a very large table. To minimise browser related problems with such a large page, we have split the table into parts. Please use the links below to view parts of the table.
Some of these entries are very recent and have not yet been evaluated.
References for these data are as follows: D.J.Parker |
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