View source for Physics:Calcium-48

{{Short description|Isotope of calcium}}
{{Infobox isotope
 | alternate_names =
 | symbol = Ca
 | mass_number = 48
 | mass = 47.952534(4)
 | num_neutrons = 28
 | num_protons = 20
 | abundance =0.187%
 | halflife = (6.4{{su|p=+0.7|b=−0.6}}{{su|p=+1.2|b=−0.9}}) × 10<sup>19</sup> a
 | image = Calcium-48 carbonate.png
 | image_caption = A glass container with 2&nbsp;g of [[Chemistry:Calcium carbonate|{{chem|48|Ca|C|O|3}}]]
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}}
'''Calcium-48''' is a scarce [[Physics:Isotopes of calcium|isotope of calcium]] containing 20 [[Physics:Proton|proton]]s and 28 [[Physics:Neutron|neutron]]s. It makes up 0.187% of natural [[Chemistry:Calcium|calcium]] by [[Chemistry:Mole fraction|mole fraction]].<ref>{{cite web| url = http://physics.nist.gov/PhysRefData/Compositions/index.html| title = Atomic Weights and Isotopic Compositions| accessdate = 2006-10-27| last = Coursey| first = J. S. |author2=D. J. Schwab |author3=R. A. Dragoset|date=February 2005| work = NIST Physical Reference Data}}</ref> Although it is unusually neutron-rich for such a light nucleus, its [[Physics:Beta decay|beta decay]] is extremely hindered, and so the only [[Physics:Radioactive decay|radioactive decay]] pathway that it has been observed to undergo is the extremely rare process of [[Physics:Double beta decay|double beta decay]]. Its [[Physics:Half-life|half-life]] is about 6.4×10<sup>19</sup>&nbsp;years,<ref name=Arnold2016>{{Cite journal
 |last1=Arnold |first1=R.
 |display-authors=0
 |year=2016
 |collaboration=NEMO-3 Collaboration
 |title= Measurement of the double-beta decay half-life and search for the neutrinoless double-beta decay of <sup>48</sup>Ca with the NEMO-3 detector
 |journal=[[Physics:Physical Review D|Physical Review D]]
 |volume=93 |issue=11
 |pages=112008
 |doi= 10.1103/PhysRevD.93.112008
|arxiv=1604.01710|bibcode=2016PhRvD..93k2008A}}</ref> so for all practical purposes it can be treated as stable. One factor contributing to this unusual stability is that 20 and 28 are both [[Physics:Magic number|magic numbers]], making <sup>48</sup>Ca a "doubly magic" nucleus.

Since <sup>48</sup>Ca is both practically stable and neutron-rich, it is a valuable starting material for the production of new nuclei in [[Physics:Particle accelerator|particle accelerator]]s, both by fragmentation<ref>{{cite journal | last = Notani | first = M. | year = 2002 | title = New neutron-rich isotopes, <sup>34</sup>Ne, <sup>37</sup>Na and <sup>43</sup>Si, produced by fragmentation of a 64A MeV <sup>48</sup>Ca beam | journal = Physics Letters B | volume = 542 | issue = 1–2 | pages = 49–54 | doi = 10.1016/S0370-2693(02)02337-7 |bibcode = 2002PhLB..542...49N |display-authors=0}}</ref> and by fusion reactions with other nuclei, for example in the discoveries of the heaviest five elements on the periodic table, from [[Chemistry:Flerovium|flerovium]] to [[Chemistry:Oganesson|oganesson]].<ref>{{cite journal | last = Oganessian | first = Yu. Ts. |date=October 2006 | title = Synthesis of the isotopes of elements 118 and 116 in the <sup>249</sup>Cf and <sup>245</sup>Cm + <sup>48</sup>Ca fusion reactions | journal = Physical Review C | volume = 74 | pages = 044602 | doi = 10.1103/PhysRevC.74.044602 | bibcode=2006PhRvC..74d4602O | issue = 4|display-authors=0| doi-access = free }}</ref> Heavier nuclei generally require a greater fraction of neutrons for maximum stability, so neutron-rich starting materials are necessary.

<sup>48</sup>Ca is the lightest nucleus known to undergo [[Physics:Double beta decay|double beta decay]] and the only one simple enough to be analyzed with the ''sd'' [[Physics:Nuclear shell model|nuclear shell model]]. It also releases more energy (4.27&nbsp;[[Physics:MeV|MeV]]) than any other double beta decay candidate.<ref name="Balysh">{{cite journal | last = Balysh | first = A. | year = 1996 | title = Double Beta Decay of <sup>48</sup>Ca | journal = Physical Review Letters | volume = 77 | pages = 5186–5189 | doi = 10.1103/PhysRevLett.77.5186 | pmid = 10062737 | issue = 26 | bibcode=1996PhRvL..77.5186B|arxiv = nucl-ex/9608001 |display-authors=0}}</ref> These properties make it an interesting probe of nuclear structure models and a promising candidate in the ongoing search for [[Physics:Neutrinoless double beta decay|neutrinoless double beta decay]].

==See also==
* [[Physics:Nickel-48|Nickel-48]]

== References ==
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[[Category:Isotopes of calcium]]

{{Sourceattribution|Calcium-48}}