# Isotopes of californium

Californium ($_{98}$Cf) 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 $^{245}$Cf in 1950. There are 20 known radioisotopes ranging from $^{237}$Cf to $^{256}$Cf and one nuclear isomer, $^{249m}$Cf. The longest-lived isotope is $^{251}$Cf with a half-life of 898 years.

## List of isotopes

| Nuclide | Z | N | Isotopic mass (Da) | Half-life | Decay mode | Daughter isotope | Spin and parity |
| Spin and parity |||
| $^{237}$Cf | 98 | 139 | 237.06220(10) | 0.8(2) s | α (70%) | $^{233}$Cm | 5/2+# |
| $^{237}$Cf | 98 | 139 | 237.06220(10) | 0.8(2) s | SF (30%) | (various) | 5/2+# |
| $^{237}$Cf | 98 | 139 | 237.06220(10) | 0.8(2) s | β$^+$ (rare) | $^{237}$Bk | 5/2+# |
| $^{238}$Cf | 98 | 140 | 238.06149(32)# | 21.1(13) ms | SF | (various) | 0+ |
| $^{238}$Cf | 98 | 140 | 238.06149(32)# | 21.1(13) ms | α (<5%) | $^{234}$Cm | 0+ |
| $^{239}$Cf | 98 | 141 | 239.06248(13)# | 28(2) s | α (65%) | $^{235}$Cm | (5/2+) |
| $^{239}$Cf | 98 | 141 | 239.06248(13)# | 28(2) s | β$^+$ (35%) | $^{239}$Bk | (5/2+) |
| $^{240}$Cf | 98 | 142 | 240.062253(19) | 40.3(9) s | α (98.5%) | $^{236}$Cm | 0+ |
| $^{240}$Cf | 98 | 142 | 240.062253(19) | 40.3(9) s | SF (1.5%) | (various) | 0+ |
| $^{240}$Cf | 98 | 142 | 240.062253(19) | 40.3(9) s | β$^+$? | $^{240}$Bk | 0+ |
| $^{241}$Cf | 98 | 143 | 241.06369(18)# | 2.35(18) min | β$^+$ (85%) | $^{241}$Bk | (7/2−) |
| $^{241}$Cf | 98 | 143 | 241.06369(18)# | 2.35(18) min | α (15%) | $^{237}$Cm | (7/2−) |
| $^{242}$Cf | 98 | 144 | 242.063755(14) | 3.49(15) min | α (61%) | $^{238}$Cm | 0+ |
| $^{242}$Cf | 98 | 144 | 242.063755(14) | 3.49(15) min | β$^+$ (39%) | $^{242}$Bk | 0+ |
| $^{242}$Cf | 98 | 144 | 242.063755(14) | 3.49(15) min | SF (<0.014%) | (various) | 0+ |
| $^{243}$Cf | 98 | 145 | 243.06548(19)# | 10.8(3) min | β$^+$ (86%) | $^{243}$Bk | (1/2+) |
| $^{243}$Cf | 98 | 145 | 243.06548(19)# | 10.8(3) min | α (14%) | $^{239}$Cm | (1/2+) |
| $^{244}$Cf | 98 | 146 | 244.0659994(28) | 19.5(5) min | α (75%) | $^{240}$Cm | 0+ |
| $^{244}$Cf | 98 | 146 | 244.0659994(28) | 19.5(5) min | EC (25%) | $^{244}$Bk | 0+ |
| $^{245}$Cf | 98 | 147 | 245.0680468(26) | 45.0(15) min | β$^+$ (64.7%) | $^{245}$Bk | 1/2+ |
| $^{245}$Cf | 98 | 147 | 245.0680468(26) | 45.0(15) min | α (35.3%) | $^{241}$Cm | 1/2+ |
| $^{245m}$Cf | 57(4) keV | 57(4) keV | 57(4) keV | >100# ns | IT | $^{245}$Cf | (7/2+) |
| $^{246}$Cf | 98 | 148 | 246.0688037(16) | 35.7(5) h | α | $^{242}$Cm | 0+ |
| $^{246}$Cf | 98 | 148 | 246.0688037(16) | 35.7(5) h | SF (2.4×10$^{−4}$%) | (various) | 0+ |
| $^{246}$Cf | 98 | 148 | 246.0688037(16) | 35.7(5) h | EC? | $^{246}$Bk | 0+ |
| $^{247}$Cf | 98 | 149 | 247.070971(15) | 3.11(3) h | EC (99.965%) | $^{247}$Bk | (7/2+) |
| $^{247}$Cf | 98 | 149 | 247.070971(15) | 3.11(3) h | α (.035%) | $^{243}$Cm | (7/2+) |
| $^{248}$Cf | 98 | 150 | 248.0721829(55) | 333.5(28) d | α (99.997%) | $^{244}$Cm | 0+ |
| $^{248}$Cf | 98 | 150 | 248.0721829(55) | 333.5(28) d | SF (.0029%) | (various) | 0+ |
| $^{249}$Cf | 98 | 151 | 249.0748504(13) | 351(2) y | α | $^{245}$Cm | 9/2− |
| $^{249}$Cf | 98 | 151 | 249.0748504(13) | 351(2) y | SF (5×10$^{−7}$%) | (various) | 9/2− |
| $^{249m}$Cf | 144.98(5) keV | 144.98(5) keV | 144.98(5) keV | 45(5) μs | IT | $^{249}$Cf | 5/2+ |
| $^{250}$Cf | 98 | 152 | 250.0764045(17) | 13.08(9) y | α (99.923%) | $^{246}$Cm | 0+ |
| $^{250}$Cf | 98 | 152 | 250.0764045(17) | 13.08(9) y | SF (.077%) | (various) | 0+ |
| $^{251}$Cf | 98 | 153 | 251.0795872(42) | 898(44) y | α | $^{247}$Cm | 1/2+ |
| $^{251m}$Cf | 370.47(3) keV | 370.47(3) keV | 370.47(3) keV | 1.3(1) μs | IT | $^{251}$Cf | 11/2− |
| $^{252}$Cf | 98 | 154 | 252.0816265(25) | 2.645(8) y | α (96.8972%) | $^{248}$Cm | 0+ |
| $^{252}$Cf | 98 | 154 | 252.0816265(25) | 2.645(8) y | SF (3.1028%) | (various) | 0+ |
| $^{253}$Cf | 98 | 155 | 253.0851337(46) | 17.81(8) d | β$^−$ (99.69%) | $^{253}$Es | (7/2+) |
| $^{253}$Cf | 98 | 155 | 253.0851337(46) | 17.81(8) d | α (.31%) | $^{249}$Cm | (7/2+) |
| $^{254}$Cf | 98 | 156 | 254.087324(12) | 60.5(2) d | SF (99.69%) | (various) | 0+ |
| $^{254}$Cf | 98 | 156 | 254.087324(12) | 60.5(2) d | α (.31%) | $^{250}$Cm | 0+ |
| $^{254}$Cf | 98 | 156 | 254.087324(12) | 60.5(2) d | β$^−$β$^−$? | $^{254}$Fm | 0+ |
| $^{255}$Cf | 98 | 157 | 255.09105(22)# | 85(18) min | β$^−$ | $^{255}$Es | (7/2+) |
| $^{255}$Cf | 98 | 157 | 255.09105(22)# | 85(18) min | SF? | (various) | (7/2+) |
| $^{255}$Cf | 98 | 157 | 255.09105(22)# | 85(18) min | α? | $^{251}$Cm | (7/2+) |
| $^{256}$Cf | 98 | 158 | 256.09344(34)# | 12.3(12) min | SF | (various) | 0+ |
| $^{256}$Cf | 98 | 158 | 256.09344(34)# | 12.3(12) min | α? | $^{252}$Cm | 0+ |
| $^{256}$Cf | 98 | 158 | 256.09344(34)# | 12.3(12) min | β$^−$β$^−$? | $^{256}$Fm | 0+ |
| This table header & footer: view ||||||||
* ↑ $^m$Cf – 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 its 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 and fission products by half-life vte :
| Actinides by decay chain | Actinides by decay chain | Actinides by decay chain | Actinides by decay chain | Half-life range (a) | Fission products of $^{235}$U by yield | Fission products of $^{235}$U by yield | Fission products of $^{235}$U by yield |
| 4n | 4n + 1 | 4n + 2 | 4n + 3 | Half-life range (a) | 4.5–7% | 0.04–1.25% | <0.001% |
| Ra$^№$ | | | | 4–6 a | | Eu$^þ$ | |
| Bk | | | | > 9 a | | | |
| Cm$^ƒ$ | Pu$^ƒ$ | Cf | Ac$^№$ | 10–29 a | Sr | Kr | Cd$^þ$ |
| U$^ƒ$ | | Pu$^ƒ$ | Cm$^ƒ$ | 29–97 a | Cs | Sm$^þ$ | Sn |
| | Cf$^ƒ$ | Am$^ƒ$ | | 141–351 a | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... |
| | Am$^ƒ$ | | Cf$^ƒ$ | 430–900 a | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... |
| | | Ra$^№$ | Bk | 1.3–1.6 ka | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... |
| Pu | Th | Cm$^ƒ$ | Am$^ƒ$ | 4.7–7.4 ka | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... |
| | Cm$^ƒ$ | Cm | | 8.3–8.5 ka | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... |
| | | | Pu$^ƒ$ | 24.1 ka | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... |
| | | Th$^№$ | Pa$^№$ | 32–76 ka | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... |
| Np$^ƒ$ | U$^ƒ$ | U$^№$ | | 150–250 ka | Tc$^₡$ | Sn |
| Cm | | Pu | | 327–375 ka | | Se$^₡$ |
| | | | | 1.33 Ma | Cs$^₡$ |
| | Np$^ƒ$ | | | 1.61–6.5 Ma | Zr | Pd |
| U | | | Cm$^ƒ$ | 15–24 Ma | | I$^₡$ |
| Pu | | | | 80 Ma | ... nor beyond 15.7 Ma | ... nor beyond 15.7 Ma | ... nor beyond 15.7 Ma |
| Th$^№$ | | U$^№$ | U$^{ƒ№}$ | 0.7–14.1 Ga | ... nor beyond 15.7 Ma | ... nor beyond 15.7 Ma | ... nor beyond 15.7 Ma |
| ₡, has thermal neutron capture cross section in the range of 8–50 barnsƒ, fissile№, primarily a naturally occurring radioactive material (NORM)þ, neutron poison (thermal neutron capture cross section greater than 3k barns) |||||||||

## Californium-252

Californium-252 (Cf-252, $^{252}$Cf) 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.
This isotope produces high neutron emissions and has a number of uses in industries such as nuclear energy, medicine, and petrochemical exploration.

### Nuclear reactors

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.

### 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 $^{252}$Cf sources to detect hazardous contents inside artillery projectiles, mortar projectiles, rockets, bombs, land mines, and improvised explosive devices (IED).

### Oil and petroleum

In the oil industry, $^{252}$Cf 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.

### Medicine

Californium-252 has also been used in the treatment of serious forms of cancer. For certain types of brain and cervical cancer, $^{252}$Cf can be used as a more cost-effective substitute for radium.