Isotopes of californium (98Cf)
Main isotopes[1][2] Decay
abun­dance half-life (t1/2) mode pro­duct
248Cf synth 333.5 d α100% 244Cm
SF<0.01% –
249Cf synth 351 y α100% 245Cm
SF≪0.01% –
250Cf synth 13.08 y α99.9% 246Cm
SF0.08% –
251Cf synth 898 y α 247Cm
252Cf synth 2.645 y α96.9% 248Cm
SF3.09% –
253Cf synth 17.81 d β−99.7% 253Es
α0.31% 249Cm
254Cf synth 60.5 d SF99.7% –
α0.31% 250Cm

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

Cf-249
Cf-251
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[3] 98 139 237.06207(54)# 0.8(2) s α (70%) 233Cm 5/2+#
SF (30%) (various)
β+ (rare) 237Bk
238Cf 98 140 238.06141(43)# 21.1(13) ms SF[n 7] (various) 0+
α (<5%)[3] 234Cm
239Cf[4] 98 141 239.06242(23)# 28(2) s α (65%) 235Cm (5/2+)
β+ (35%) 239Bk
240Cf[5] 98 142 240.06230(22)# 40.3(9) s α (98.5%) 236Cm 0+
SF (1.5%) (various)
β+? 240Bk
241Cf[5] 98 143 241.06373(27)# 2.35(18) min β+ (85%) 241Bk (7/2−)
α (15%) 237Cm
242Cf[5] 98 144 242.06370(4) 3.49(15) min α (61%) 238Cm 0+
β+ (39%) 242Bk
SF (<0.014%) (various)
243Cf[5] 98 145 243.06543(15)# 10.8(3) min β+ (86%) 243Bk (1/2+)
α (14%) 239Cm
244Cf[5] 98 146 244.066001(3) 19.5(5) min α (75%) 240Cm 0+
EC (25%) 244Bk
245Cf[5] 98 147 245.068049(3) 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 98 148 246.0688053(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
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[n 11] (various) 0+
This table header & footer:
  1. ^ mCf – Excited nuclear isomer.
  2. ^ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
  3. ^ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
  4. ^ Modes of decay:
    EC: Electron capture
    SF: Spontaneous fission
  5. ^ ( ) spin value – Indicates spin with weak assignment arguments.
  6. ^ # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  7. ^ Lightest nuclide known to undergo spontaneous fission as the main decay mode
  8. ^ High neutron cross-section, tends to absorb neutrons
  9. ^ Most common isotope
  10. ^ High neutron emitter, average 3.7 neutrons per fission
  11. ^ Theoretically capable of α decay to 252Cm of β-β- decay to 256Fm[5]

Actinides vs fission products

Actinides and fission products by half-life
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 in the range of 100 a–210 ka ...

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

Californium-252

production diagram

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

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).[12][13]

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.[14]

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.[15]

References

  1. ^ CRC 2006, p. 11.196.
  2. ^ Sonzogni, Alejandro A. (Database Manager), ed. (2008). "Chart of Nuclides". National Nuclear Data Center, Brookhaven National Laboratory. Retrieved 1 March 2010.
  3. ^ a b Khuyagbaatar, J.; Heßberger, F. P.; Hofmann, S.; Ackermann, D.; Comas, V. S.; Heinz, S.; Heredia, J. A.; Kindler, B.; Kojouharov, I.; Lommel, B.; Mann, R.; Nishio, K.; Yakushev, A. (1 October 2010). "The new isotope 236Cm and new data on 233Cm and 237, 238, 240Cf" (PDF). The European Physical Journal A. 46 (1): 59–67. Bibcode:2010EPJA...46...59K. doi:10.1140/epja/i2010-11026-9. ISSN 1434-601X. S2CID 122809010. Retrieved 23 June 2023.
  4. ^ Khuyagbaatar, J.; Heßberger, F. P.; Hofmann, S.; Ackermann, D.; Burkhard, H. G.; Heinz, S.; Kindler, B.; Kojouharov, I.; Lommel, B.; Mann, R.; Maurer, J.; Nishio, K. (12 October 2020). "α decay of Fm 243 143 and Fm 245 145 , and of their daughter nuclei". Physical Review C. 102 (4): 044312. doi:10.1103/PhysRevC.102.044312. ISSN 2469-9985. S2CID 241259726. Retrieved 24 June 2023.
  5. ^ a b c d e f g Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  6. ^ 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.
  7. ^ Specifically from thermal neutron fission of uranium-235, e.g. in a typical nuclear reactor.
  8. ^ 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]."
  9. ^ This is the heaviest nuclide with a half-life of at least four years before the "sea of instability".
  10. ^ 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.
  11. ^ 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.
  12. ^ "Portable Isotopic Neutron Spectroscopy (PINS) for the Military". Frontier Technology Corp. Archived from the original on 2018-06-16. Retrieved 2016-02-24.
  13. ^ 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.
  14. ^ "Californium-252 & Antimony-Beryllium Sources". Frontier Technology Corp. Retrieved 2016-02-24.
  15. ^ 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.

Sources

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