Isotopes of californium

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.

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

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List of isotopes

Cf-249

Cf-251

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
This table header & footer: view

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 its 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

Actinides vs fission products

Actinides and fission products by half-life v t e
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
248Bk[8]				> 9 a
244Cmƒ	241Puƒ	250Cf	227Ac№	10–29 a	90Sr	85Kr	113mCdþ
232Uƒ		238Puƒ	243Cmƒ	29–97 a	137Cs	151Smþ	121mSn
	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₡
				1.33 Ma	135Cs₡
	237Npƒ			1.61–6.5 Ma	93Zr	107Pd
236U			247Cmƒ	15–24 Ma		129I₡
244Pu				80 Ma	... nor beyond 15.7 Ma[10]
232Th№		238U№	235Uƒ№	0.7–14.1 Ga
₡,  has thermal neutron capture cross section in the range of 8–50 barns ƒ,  fissile №,  primarily a naturally occurring radioactive material (NORM) þ,  neutron poison (thermal neutron capture cross section greater than 3k barns)

Californium-252

Californium-252 production diagram

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.^[11]

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 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

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.^[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. Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
4. 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.
5. 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.
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 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

• Lide, David R., ed. (2006). Handbook of Chemistry and Physics (87th ed.). CRC Press, Taylor & Francis Group. ISBN 978-0-8493-0487-3.