A doubly-magic nucleus has both protons and neutrons in magic numbers. Scientists have found that if an atomic nucleus has either protons or neutrons in certain numbers-2, 8, 20, 28, 50, 82, or 126-they arrange themselves in complete shells and make the nucleus more strongly bound than their neighbors. The results were published this week in Nature Physics.Ĭalcium, at number 20 on the periodic table, has 20 protons, which places it squarely in the “magic” numbers of nuclear physics. Nuclear theorists from UT and Oak Ridge National Laboratory are among the researchers who have found that Calcium-52 doesn’t quite have the magic scientists once thought. Image: COLLAPS Collaboration/Ronald Fernando Garcia Ruiz. The first measurement of the charge radius in Ca-52 yielded an unexpectedly large result. The “doubly magic” isotopes with mass numbers 40 (Ca-40) and 48 (Ca-48) exhibit equal charge radii. Encyclopedia of Earth, National Council for Science and the Environment, Washington, D.C.The image above shows the chain of the studied calcium isotopes. "Production of very neutron rich isotopes: What should we know?". "Shell-model study of the highly forbidden beta decay 48Ca → 48Sc". "The AME2016 atomic mass evaluation (II). "The NUBASE2016 evaluation of nuclear properties" (PDF). ^ Half-life, decay mode, nuclear spin, and isotopic composition is sourced in:Īudi, G."Standard atomic weights of the elements 2021 (IUPAC Technical Report)". ^ Prohaska, Thomas Irrgeher, Johanna Benefield, Jacqueline et al."The NUBASE2020 evaluation of nuclear properties" (PDF). ^ Theorized to also undergo β − decay to 48Sc with a partial half-life exceeding 1.1 +0.8.^ Lightest nuclide known to undergo double beta decay.^ Believed to be capable of undergoing triple beta decay with very long partial half-life.^ Believed to undergo β −β − decay to 46Ti with a half-life no less than 2.8×10 15 y.^ Believed to undergo double electron capture to 40Ar with a half-life no less than 5.9×10 21 y.^ Heaviest nuclide with equal numbers of protons and neutrons with no observed decay.^ # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN). ^ ( ) spin value – Indicates spin with weak assignment arguments.^ Bold symbol as daughter – Daughter product is stable.^ Bold half-life – nearly stable, half-life longer than age of universe.^ ( ) – Uncertainty (1 σ) is given in concise form in parentheses after the corresponding last digits.List of isotopes Around 2 g of calcium-48 Nuclide Techniques using mass spectrometry and a double spike isotope dilution have been used for K–Ca age dating. While K–Ar dating has been used extensively in the geological sciences, the prevalence of 40Ca in nature has impeded its use in dating. 40Ca is also one of the daughter products of 40K decay, along with 40Ar. Ĥ0Ca comprises about 97% of naturally occurring calcium. All other calcium isotopes have half-lives measured in minutes or less. The most stable artificial radioisotopes are 45Ca with a half-life of 163 days and 47Ca with a half-life of 4.5 days. 41Ca has received much attention in stellar studies because it decays to 41K, a critical indicator of solar system anomalies. Most of its production is in the upper metre of the soil column, where the cosmogenic neutron flux is still sufficiently strong. Unlike cosmogenic isotopes that are produced in the atmosphere, 41Ca is produced by neutron activation of 40Ca. Calcium also has a cosmogenic isotope, radioactive 41Ca, which has a half-life of 99,400 years. The most abundant isotope, 40Ca, as well as the rare 46Ca, are theoretically unstable on energetic grounds, but their decay has not been observed. There are five stable isotopes ( 40Ca, 42Ca, 43Ca, 44Ca and 46Ca), plus one isotope ( 48Ca) with such a long half-life that for all practical purposes it can be considered stable. Calcium ( 20Ca) has 26 known isotopes, ranging from 35Ca to 60Ca.
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