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.
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List of isotopes
| Nuclide [n 1] | Z | N | Isotopic mass (Da)[3] [n 2][n 3] | Half-life[4] | Decay mode[4] [n 4] | Daughter isotope | Spin and parity[4] [n 5][n 6] | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Excitation energy | |||||||||||||||||||
| 237Cf | 98 | 139 | 237.06220(10) | 0.8(2) s | α (70%) | 233Cm | 5/2+# | ||||||||||||
| SF (30%) | (various) | ||||||||||||||||||
| β+ (rare) | 237Bk | ||||||||||||||||||
| 238Cf | 98 | 140 | 238.06149(32)# | 21.1(13) ms | SF[n 7] | (various) | 0+ | ||||||||||||
| α (<5%) | 234Cm | ||||||||||||||||||
| 239Cf[5] | 98 | 141 | 239.06248(13)# | 28(2) s | α (65%) | 235Cm | (5/2+) | ||||||||||||
| β+ (35%) | 239Bk | ||||||||||||||||||
| 240Cf | 98 | 142 | 240.062253(19) | 40.3(9) s | α (98.5%) | 236Cm | 0+ | ||||||||||||
| SF (1.5%) | (various) | ||||||||||||||||||
| β+? | 240Bk | ||||||||||||||||||
| 241Cf[5] | 98 | 143 | 241.06369(18)# | 2.35(18) min | β+ (85%) | 241Bk | (7/2−) | ||||||||||||
| α (15%) | 237Cm | ||||||||||||||||||
| 242Cf | 98 | 144 | 242.063755(14) | 3.49(15) min | α (61%) | 238Cm | 0+ | ||||||||||||
| β+ (39%) | 242Bk | ||||||||||||||||||
| SF (<0.014%) | (various) | ||||||||||||||||||
| 243Cf | 98 | 145 | 243.06548(19)# | 10.8(3) min | β+ (86%) | 243Bk | (1/2+) | ||||||||||||
| α (14%) | 239Cm | ||||||||||||||||||
| 244Cf | 98 | 146 | 244.0659994(28) | 19.5(5) min | α (75%) | 240Cm | 0+ | ||||||||||||
| EC (25%) | 244Bk | ||||||||||||||||||
| 245Cf | 98 | 147 | 245.0680468(26) | 45.0(15) min | β+ (64.7%) | 245Bk | 1/2+ | ||||||||||||
| α (35.3%) | 241Cm | ||||||||||||||||||
| 245mCf | 57(4) keV | >100# ns | IT | 245Cf | (7/2+) | ||||||||||||||
| 246Cf | 98 | 148 | 246.0688037(16) | 35.7(5) h | α | 242Cm | 0+ | ||||||||||||
| SF (2.4×10−4%) | (various) | ||||||||||||||||||
| EC? | 246Bk | ||||||||||||||||||
| 247Cf | 98 | 149 | 247.070971(15) | 3.11(3) h | EC (99.965%) | 247Bk | (7/2+) | ||||||||||||
| α (.035%) | 243Cm | ||||||||||||||||||
| 248Cf | 98 | 150 | 248.0721829(55) | 333.5(28) d | α (99.997%) | 244Cm | 0+ | ||||||||||||
| SF (.0029%) | (various) | ||||||||||||||||||
| 249Cf | 98 | 151 | 249.0748504(13) | 351(2) y | α | 245Cm | 9/2− | ||||||||||||
| SF (5×10−7%) | (various) | ||||||||||||||||||
| 249mCf | 144.98(5) keV | 45(5) μs | IT | 249Cf | 5/2+ | ||||||||||||||
| 250Cf | 98 | 152 | 250.0764045(17) | 13.08(9) y | α (99.923%) | 246Cm | 0+ | ||||||||||||
| SF (.077%) | (various) | ||||||||||||||||||
| 251Cf[n 8] | 98 | 153 | 251.0795872(42) | 898(44) y | α | 247Cm | 1/2+ | ||||||||||||
| 251mCf | 370.47(3) keV | 1.3(1) μs | IT | 251Cf | 11/2− | ||||||||||||||
| 252Cf[n 9] | 98 | 154 | 252.0816265(25) | 2.645(8) y | α (96.8972%) | 248Cm | 0+ | ||||||||||||
| SF (3.1028%)[n 10] | (various) | ||||||||||||||||||
| 253Cf | 98 | 155 | 253.0851337(46) | 17.81(8) d | β− (99.69%) | 253Es | (7/2+) | ||||||||||||
| α (.31%) | 249Cm | ||||||||||||||||||
| 254Cf | 98 | 156 | 254.087324(12) | 60.5(2) d | SF (99.69%) | (various) | 0+ | ||||||||||||
| α (.31%) | 250Cm | ||||||||||||||||||
| β−β−? | 254Fm | ||||||||||||||||||
| 255Cf | 98 | 157 | 255.09105(22)# | 85(18) min | β− | 255Es | (7/2+) | ||||||||||||
| SF? | (various) | ||||||||||||||||||
| α? | 251Cm | ||||||||||||||||||
| 256Cf | 98 | 158 | 256.09344(34)# | 12.3(12) min | SF | (various) | 0+ | ||||||||||||
| α? | 252Cm | ||||||||||||||||||
| β−β−? | 256Fm | ||||||||||||||||||
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Actinides vs fission products
| Actinides[6] by decay chain | Half-life range (a) | Fission products of 235U by yield[7] | ||||||
|---|---|---|---|---|---|---|---|---|
| 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[8] | 249Cfƒ | 242mAmƒ | 141–351 a | No fission products have a half-life | ||||
| 241Amƒ | 251Cfƒ[9] | 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[10] | ||||||
| 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.[11]
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
Neutron sources using 252Cf are most notably used in the start-up of nuclear reactors. Once a reactor is filled with nuclear fuel, the stable neutron emission from the source material starts the chain reaction.
Military and defense
The portable isotopic neutron spectroscopy (PINS) used by United States Armed Forces, the National Guard, Homeland Security, and Customs and Border Protection, uses 252Cf sources to detect hazardous contents inside artillery projectiles, mortar projectiles, rockets, bombs, land mines, and improvised explosive devices (IED).[12][13]
Oil and petroleum
In the oil industry, 252Cf is 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.[14]
Medicine
252Cf has also been used in the treatment of serious forms of cancer. For certain types of brain and cervical cancer, 252Cf can be used as a more cost-effective substitute for radium.[15]
References
Sources
- Lide, David R., ed. (2006). Handbook of Chemistry and Physics (87th ed.). CRC Press, Taylor & Francis Group. ISBN 978-0-8493-0487-3.