Calcium-48

Calcium-48 is a scarce <a href="/facts/Isotope_of_calcium/YhuBa6LI">isotope of calcium</a> containing 20 <a href="/facts/Proton/clCjepXP">protons</a> and 28 <a href="/facts/Neutron/oRCM1geb">neutrons</a>. It makes up 0.187% of natural <a href="/facts/Calcium/hf252CC0">calcium</a> by <a href="/facts/Mole_fraction/nW4EepmJ">mole fraction</a>. Although it is unusually neutron-rich for such a light nucleus, its <a href="/facts/Beta_decay/vxTBlckp">beta decay</a> is extremely hindered, and so the only <a href="/facts/Radioactive_decay/Ya6FVjt4">radioactive decay</a> pathway that it has been observed to undergo is the extremely rare <a href="/facts/Double_beta_decay/ILmpbfqS">double beta decay</a> (2β). Its <a href="/facts/Half-life/kGVH8BAB">half-life</a> is about 6.4×1019 years, so for all practical purposes it can be treated as stable. One cause of this unusual stability is that 20 and 28 are both <a href="/facts/Magic_number_(physics)/v9PwXFzQ">magic numbers</a>, making 48Ca a "doubly magic" nucleus.
Since 48Ca is both practically stable and neutron-rich, it is a valuable starting material for the production of new nuclei in <a href="/facts/Particle_accelerator/Pkuc08xC">particle accelerators</a>, both by fragmentation and by fusion reactions with other nuclei, for example in the discoveries of the five heaviest known elements, from <a href="/facts/Flerovium/Aa7uGMuG">flerovium</a> to <a href="/facts/Oganesson/zs5MQDjV">oganesson</a> (<a href="/facts/Atomic_number/bgAr581S">atomic numbers</a> 114 through 118). 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 the sd <a href="/facts/Nuclear_shell_model/1Qgep495">nuclear shell model</a>. It also releases more energy (4.27 <a href="/facts/MeV/YMT1fqX9">MeV</a>) than any other 2β candidate. These properties make it an interesting probe of nuclear structure models and a promising candidate in the ongoing search for <a href="/facts/Neutrinoless_double_beta_decay/7u36G9d4">neutrinoless double beta decay</a>.

Calcium-48 open-in-new

Calcium-48