 A glass container with 2 g of48 CaCO 3 | |
| General | |
|---|---|
| Symbol | 48Ca |
| Names | calcium-48, 48Ca, Ca-48 |
| Protons(Z) | 20 |
| Neutrons(N) | 28 |
| Nuclide data | |
| Natural abundance | 0.187% |
| Half-life(t1/2) | (6.4+0.7 −0.6+1.2 −0.9) × 1019 a |
| Isotope mass | 47.952534(4)Da |
| Isotopes of calcium Complete table of nuclides | |
Calcium-48 is a scarceisotope of calcium containing 20protons and 28neutrons. It makes up 0.187% of naturalcalcium bymole fraction.[1] Although it is unusually neutron-rich for such a light nucleus, itsbeta decay is extremely hindered, and so the onlyradioactive decay pathway that it has been observed to undergo is the extremely raredouble beta decay (2β). Itshalf-life is about 6.4×1019 years,[2] so for all practical purposes it can be treated as stable. One cause of this unusual stability is that 20 and 28 are bothmagic numbers, making48Ca a "doubly magic" nucleus.
Since48Ca is both practically stable and neutron-rich, it is a valuable starting material for the production of new nuclei inparticle accelerators, both by fragmentation[3] and by fusion reactions with other nuclei, for example in the discoveries of the five heaviest known elements, fromflerovium tooganesson (atomic numbers 114 through 118).[4] Heavier nuclei generally require a greater fraction of neutrons for maximum stability, so neutron-rich starting materials are necessary.
48Ca is the lightest nucleus known to undergo 2β and the only one simple enough to be analyzed with thesdnuclear shell model. It also releases more energy (4.27 MeV) than any other 2β candidate.[5] These properties make it an interesting probe of nuclear structure models and a promising candidate in the ongoing search forneutrinoless double beta decay.