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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.
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) | ||||||||||||||||||
238Cf | 98 | 140 | 238.06149(32)# | 21.1(13) ms | SF (97.5%) [n 7] | (various) | 0+ | ||||||||||||
α (2.5%) | 234Cm | ||||||||||||||||||
239Cf | 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) | ||||||||||||||||||
241Cf | 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) | ||||||||||||||||||
247Cf | 98 | 149 | 247.070971(15) | 3.11(3) h | EC (99.965%) | 247Bk | (7/2+) | ||||||||||||
α (0.035%) | 243Cm | ||||||||||||||||||
248Cf | 98 | 150 | 248.072183(5) | 333.5(28) d | α | 244Cm | 0+ | ||||||||||||
SF (0.0029%) | (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 (0.077%) | (various) | ||||||||||||||||||
251Cf [n 8] | 98 | 153 | 251.079587(4) | 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 | 253.085134(5) | 17.81(8) d | β− (99.69%) | 253Es | (7/2+) | ||||||||||||
α (0.31%) | 249Cm | ||||||||||||||||||
254Cf [n 11] | 98 | 156 | 254.087324(12) | 60.5(2) d | SF (99.69%) | (various) | 0+ | ||||||||||||
α (0.31%) | 250Cm | ||||||||||||||||||
255Cf | 98 | 157 | 255.09105(22)# | 85(18) min | β− | 255Es | (7/2+) | ||||||||||||
256Cf [n 12] | 98 | 158 | 256.09344(34)# | 12.3(12) min | SF | (various) | 0+ | ||||||||||||
This table header & footer: |
EC: | Electron capture |
SF: | Spontaneous fission |
Actinides [5] by decay chain | Half-life range (a) | Fission products of 235U by yield [6] | ||||||
---|---|---|---|---|---|---|---|---|
4n | 4n + 1 | 4n + 2 | 4n + 3 | 4.5–7% | 0.04–1.25% | <0.001% | ||
228 Ra№ | 4–6 a | 155 Euþ | ||||||
248 Bk [7] | > 9 a | |||||||
244 Cmƒ | 241 Puƒ | 250 Cf | 227 Ac№ | 10–29 a | 90 Sr | 85 Kr | 113m Cdþ | |
232 Uƒ | 238 Puƒ | 243 Cmƒ | 29–97 a | 137 Cs | 151 Smþ | 121m Sn | ||
249 Cfƒ | 242m Amƒ | 141–351 a | No fission products have a half-life | |||||
241 Amƒ | 251 Cfƒ [8] | 430–900 a | ||||||
226 Ra№ | 247 Bk | 1.3–1.6 ka | ||||||
240 Pu | 229 Th | 246 Cmƒ | 243 Amƒ | 4.7–7.4 ka | ||||
245 Cmƒ | 250 Cm | 8.3–8.5 ka | ||||||
239 Puƒ | 24.1 ka | |||||||
230 Th№ | 231 Pa№ | 32–76 ka | ||||||
236 Npƒ | 233 Uƒ | 234 U№ | 150–250 ka | 99 Tc₡ | 126 Sn | |||
248 Cm | 242 Pu | 327–375 ka | 79 Se₡ | |||||
1.33 Ma | 135 Cs₡ | |||||||
237 Npƒ | 1.61–6.5 Ma | 93 Zr | 107 Pd | |||||
236 U | 247 Cmƒ | 15–24 Ma | 129 I₡ | |||||
244 Pu | 80 Ma | ... nor beyond 15.7 Ma [9] | ||||||
232 Th№ | 238 U№ | 235 Uƒ№ | 0.7–14.1 Ga | |||||
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Californium-252 (Cf-252, 252Cf) undergoes spontaneous fission with a branching ratio of 3.09% and is used in small 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. [10]
This isotope produces high neutron emissions and has a number of uses in industries such as nuclear energy, medicine, and petrochemical exploration.
Californium-252 neutron sources are most notably used in the start-up of nuclear reactors. Once a reactor is filled with nuclear fuel, the stable neutron emission from said source starts the chain reaction.
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). [11] [12]
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. [13]
Californium-252 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. [14]