Isotopes of californium
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Californium (98Cf) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 245Cf in 1950. There are 20 known radioisotopes ranging from 237Cf to 256Cf and one nuclear isomer, 249mCf. The longest-lived isotope is 251Cf with a half-life of 898 years.
List of isotopes
Nuclide [n 1] |
Z | N | Isotopic mass (Da) [n 2][n 3] |
Half-life |
Decay mode [n 4] |
Daughter isotope |
Spin and parity [n 5][n 6] | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Excitation energy | |||||||||||||||||||
237Cf | 98 | 139 | 237.06207(54)# | 2.1(3) s | SF | (various) | 5/2+# | ||||||||||||
β+ | 237Bk | ||||||||||||||||||
α | 233Cm | ||||||||||||||||||
238Cf | 98 | 140 | 238.06141(43)# | 21.1(13) ms | SF[n 7] | (various) | 0+ | ||||||||||||
β+ (rare) | 238Bk | ||||||||||||||||||
α (rare) | 234Cm | ||||||||||||||||||
239Cf | 98 | 141 | 239.06242(23)# | 60(30) s [39(+37−12) s] |
α | 235Cm | 5/2+# | ||||||||||||
β+ (rare) | 239Bk | ||||||||||||||||||
240Cf | 98 | 142 | 240.06230(22)# | 1.06(15) min | α (98%) | 236Cm | 0+ | ||||||||||||
SF (2%) | (various) | ||||||||||||||||||
β+ (rare) | 240Bk | ||||||||||||||||||
241Cf | 98 | 143 | 241.06373(27)# | 3.78(70) min | β+ (75%) | 241Bk | 7/2−# | ||||||||||||
α (25%) | 237Cm | ||||||||||||||||||
242Cf | 98 | 144 | 242.06370(4) | 3.49(15) min | α (80%) | 238Cm | 0+ | ||||||||||||
β+ (20%) | 242Bk | ||||||||||||||||||
SF (.014%) | (various) | ||||||||||||||||||
243Cf | 98 | 145 | 243.06543(15)# | 10.7(5) min | β+ (86%) | 243Bk | (1/2+) | ||||||||||||
α (14%) | 239Cm | ||||||||||||||||||
244Cf | 98 | 146 | 244.066001(3) | 19.4(6) min | α (99%) | 240Cm | 0+ | ||||||||||||
EC (1%) | 244Bk | ||||||||||||||||||
245Cf | 98 | 147 | 245.068049(3) | 45.0(15) min | β+ (64%) | 245Bk | (5/2+) | ||||||||||||
α (36%) | 241Cm | ||||||||||||||||||
246Cf | 98 | 148 | 246.0688053(22) | 35.7(5) h | α | 242Cm | 0+ | ||||||||||||
EC (5×10−4%) | 246Bk | ||||||||||||||||||
SF (2×10−4%) | (various) | ||||||||||||||||||
247Cf | 98 | 149 | 247.071001(9) | 3.11(3) h | EC (99.96%) | 247Bk | (7/2+)# | ||||||||||||
α (.04%) | 243Cm | ||||||||||||||||||
248Cf | 98 | 150 | 248.072185(6) | 333.5(28) d | α (99.99%) | 244Cm | 0+ | ||||||||||||
SF (.0029%) | (various) | ||||||||||||||||||
249Cf | 98 | 151 | 249.0748535(24) | 351(2) y | α | 245Cm | 9/2− | ||||||||||||
SF (5×10−7%) | (various) | ||||||||||||||||||
249mCf | 144.98(5) keV | 45(5) μs | 5/2+ | ||||||||||||||||
250Cf | 98 | 152 | 250.0764061(22) | 13.08(9) y | α (99.92%) | 246Cm | 0+ | ||||||||||||
SF (.077%) | (various) | ||||||||||||||||||
251Cf[n 8] | 98 | 153 | 251.079587(5) | 900(40) y | α | 247Cm | 1/2+ | ||||||||||||
252Cf[n 9] | 98 | 154 | 252.081626(5) | 2.645(8) y | α (96.9%) | 248Cm | 0+ | ||||||||||||
SF (3.09%)[n 10] | (various) | ||||||||||||||||||
253Cf | 98 | 155 | 253.085133(7) | 17.81(8) d | β− (99.69%) | 253Es | (7/2+) | ||||||||||||
α (.31%) | 249Cm | ||||||||||||||||||
254Cf | 98 | 156 | 254.087323(13) | 60.5(2) d | SF (99.69%) | (various) | 0+ | ||||||||||||
α (.31%) | 250Cm | ||||||||||||||||||
β−β− (rare) | 254Fm | ||||||||||||||||||
255Cf | 98 | 157 | 255.09105(22)# | 85(18) min | β− (99.99%) | 255Es | (7/2+) | ||||||||||||
SF (.001%) | (various) | ||||||||||||||||||
α (10−5%) | 251Cm | ||||||||||||||||||
256Cf | 98 | 158 | 256.09344(32)# | 12.3(12) min | SF (~100%) | (various) | 0+ | ||||||||||||
α (10−6%) | 252Cm | ||||||||||||||||||
β−β− (rare) | 256Fm | ||||||||||||||||||
This table header & footer: |
- ^ mCf – Excited nuclear isomer.
- ^ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
- ^ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
- ^
Modes of decay:
EC: Electron capture SF: Spontaneous fission - ^ ( ) spin value – Indicates spin with weak assignment arguments.
- ^ # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
- ^ Lightest nuclide known to undergo spontaneous fission as the main decay mode
- ^ High neutron cross-section, tends to absorb neutrons
- ^ Most common isotope
- ^ High neutron emitter, average 3.7 neutrons per fission
Actinides vs fission products
Actinides[1] by decay chain | Half-life range (a) |
Fission products of 235U by yield[2] | ||||||
---|---|---|---|---|---|---|---|---|
4n | 4n + 1 | 4n + 2 | 4n + 3 | 4.5–7% | 0.04–1.25% | <0.001% | ||
228Ra№ | 4–6 a | 155Euþ | ||||||
244Cmƒ | 241Puƒ | 250Cf | 227Ac№ | 10–29 a | 90Sr | 85Kr | 113mCdþ | |
232Uƒ | 238Puƒ | 243Cmƒ | 29–97 a | 137Cs | 151Smþ | 121mSn | ||
248Bk[3] | 249Cfƒ | 242mAmƒ | 141–351 a |
No fission products have a half-life in the range of 100 a–210 ka ... | ||||
241Amƒ | 251Cfƒ[4] | 430–900 a | ||||||
226Ra№ | 247Bk | 1.3–1.6 ka | ||||||
240Pu | 229Th | 246Cmƒ | 243Amƒ | 4.7–7.4 ka | ||||
245Cmƒ | 250Cm | 8.3–8.5 ka | ||||||
239Puƒ | 24.1 ka | |||||||
230Th№ | 231Pa№ | 32–76 ka | ||||||
236Npƒ | 233Uƒ | 234U№ | 150–250 ka | 99Tc₡ | 126Sn | |||
248Cm | 242Pu | 327–375 ka | 79Se₡ | |||||
1.53 Ma | 93Zr | |||||||
237Npƒ | 2.1–6.5 Ma | 135Cs₡ | 107Pd | |||||
236U | 247Cmƒ | 15–24 Ma | 129I₡ | |||||
244Pu | 80 Ma |
... nor beyond 15.7 Ma[5] | ||||||
232Th№ | 238U№ | 235Uƒ№ | 0.7–14.1 Ga | |||||
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Californium-252
Californium-252 (Cf-252, 252Cf) undergoes spontaneous fission with a branching ratio of 3.09% and is used in small sized neutron sources. Fission neutrons have an energy range of 0 to 13 MeV with a mean value of 2.3 MeV and a most probable value of 1 MeV.[6]
This isotope produces high neutron emissions and can be used for a number of applications in industries such as nuclear energy, medicine, and petrochemical exploration.
Nuclear reactors
The neutron sources produced from 252Cf are most notably used in the start-up of nuclear reactors. Once a reactor is filled with nuclear fuel, the stable neutron emissions from the source material initiates the fission chain reaction.
Military and defense
The portable isotopic neutron spectroscopy (PINS) used by United States Armed Forces, the National Guard, Homeland Security, and U.S. Customs and Border Protection, employs the use of 252Cf sources to detect hazardous contents found inside artillery projectiles, mortar projectiles, rockets, bombs, land mines, and improvised explosive devices (IED).[7][8]
Oil and petroleum
In the oil industry, 252Cf neutron sources are used to find layers of petroleum and water in a well. Instrumentation is lowered into the well which bombards the formation with high energy neutrons to determine porosity, permeability, and hydrocarbon presence along the length of the borehole.[9]
Medicine
Californium-252 has also been used in the treatment of serious forms of cancer. In patients with certain types of brain and cervical cancer, 252Cf can be used as a more cost-effective substitute for radium.[10]
References
- ^ Plus radium (element 88). While actually a sub-actinide, it immediately precedes actinium (89) and follows a three-element gap of instability after polonium (84) where no nuclides have half-lives of at least four years (the longest-lived nuclide in the gap is radon-222 with a half life of less than four days). Radium's longest lived isotope, at 1,600 years, thus merits the element's inclusion here.
- ^ Specifically from thermal neutron fission of uranium-235, e.g. in a typical nuclear reactor.
- ^ Milsted, J.; Friedman, A. M.; Stevens, C. M. (1965). "The alpha half-life of berkelium-247; a new long-lived isomer of berkelium-248". Nuclear Physics. 71 (2): 299. Bibcode:1965NucPh..71..299M. doi:10.1016/0029-5582(65)90719-4.
"The isotopic analyses disclosed a species of mass 248 in constant abundance in three samples analysed over a period of about 10 months. This was ascribed to an isomer of Bk248 with a half-life greater than 9 [years]. No growth of Cf248 was detected, and a lower limit for the β− half-life can be set at about 104 [years]. No alpha activity attributable to the new isomer has been detected; the alpha half-life is probably greater than 300 [years]." - ^ This is the heaviest nuclide with a half-life of at least four years before the "sea of instability".
- ^ Excluding those "classically stable" nuclides with half-lives significantly in excess of 232Th; e.g., while 113mCd has a half-life of only fourteen years, that of 113Cd is nearly eight quadrillion years.
- ^ Dicello, J. F.; Gross, W.; Kraljevic, U. (1972). "Radiation Quality of Californium-252". Physics in Medicine and Biology. 17 (3): 345–355. Bibcode:1972PMB....17..345D. doi:10.1088/0031-9155/17/3/301. PMID 5070445. S2CID 250786668.
- ^ "Portable Isotopic Neutron Spectroscopy (PINS) for the Military". Frontier Technology Corp. Retrieved 2016-02-24.
- ^ Martin, R. C.; Knauer, J. B.; Balo, P. A. (2000-11-01). "Production, distribution and applications of californium-252 neutron sources". Applied Radiation and Isotopes. 53 (4–5): 785–792. doi:10.1016/s0969-8043(00)00214-1. ISSN 0969-8043. PMID 11003521.
- ^ "Californium-252 & Antimony-Beryllium Sources". Frontier Technology Corp. Retrieved 2016-02-24.
- ^ Maruyama, Y.; van Nagell, J. R.; Yoneda, J.; Donaldson, E.; Hanson, M.; Martin, A.; Wilson, L. C.; Coffey, C. W.; Feola, J. (1984-10-01). "Five-year cure of cervical cancer treated using californium-252 neutron brachytherapy". American Journal of Clinical Oncology. 7 (5): 487–493. doi:10.1097/00000421-198410000-00018. ISSN 0277-3732. PMID 6391143. S2CID 12553815.
- Isotope masses from:
- Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
- Isotopic compositions and standard atomic masses from:
- de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
- Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051.
- "News & Notices: Standard Atomic Weights Revised". International Union of Pure and Applied Chemistry. 19 October 2005.
- Half-life, spin, and isomer data selected from the following sources.
- Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
- National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
- Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.