Isotopes of californium: Difference between revisions

Isotopes of californium (₉₈Cf)
SF<0.01%	–
SF≪0.01%	–
SF0.08%	–
SF3.09%	–
α0.31%	249Cm
α0.31%	250Cm
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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.

List of isotopes

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]}
Nuclide ^{[n 1]}	Excitation energy			Half-life	Decay mode ^{[n 4]}	Daughter isotope	Spin and parity ^{[n 5]}^{[n 6]}
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+
²³⁸Cf	98	140	238.06141(43)#	21.1(13) ms	α (<5%)^[4]	²³⁴Cm	0+
²³⁹Cf^[5]	98	141	239.06242(23)#	28(2) s	α (65%)	²³⁵Cm	(5/2+)
²³⁹Cf^[5]	98	141	239.06242(23)#	28(2) s	β⁺ (35%)	²³⁹Bk	(5/2+)
²⁴⁰Cf^[6]	98	142	240.06230(22)#	40.3(9) s	α (98.5%)	²³⁶Cm	0+
					SF (1.5%)	(various)
					β⁺?	²⁴⁰Bk
²⁴¹Cf^[7]	98	143	241.06373(27)#	2.35(18) min	β⁺ (85%)	²⁴¹Bk	(7/2−)
²⁴¹Cf^[7]	98	143	241.06373(27)#	2.35(18) min	α (15%)	²³⁷Cm	(7/2−)
²⁴²Cf^[8]	98	144	242.06370(4)	3.49(15) min	α (61%)	²³⁸Cm	0+
					β⁺ (39%)	²⁴²Bk
					SF (<0.014%)	(various)
²⁴³Cf^[9]	98	145	243.06543(15)#	10.8(3) min	β⁺ (86%)	²⁴³Bk	(1/2+)
²⁴³Cf^[9]	98	145	243.06543(15)#	10.8(3) min	α (14%)	²³⁹Cm	(1/2+)
²⁴⁴Cf^[10]	98	146	244.066001(3)	19.5(5) min	α (75%)	²⁴⁰Cm	0+
²⁴⁴Cf^[10]	98	146	244.066001(3)	19.5(5) min	EC (25%)	²⁴⁴Bk	0+
²⁴⁵Cf^[11]	98	147	245.068049(3)	45.0(15) min	β⁺ (64.7%)	²⁴⁵Bk	1/2+
²⁴⁵Cf^[11]	98	147	245.068049(3)	45.0(15) min	α (35.3%)	²⁴¹Cm	1/2+
^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+)#
²⁴⁷Cf	98	149	247.071001(9)	3.11(3) h	α (.04%)	²⁴³Cm	(7/2+)#
²⁴⁸Cf	98	150	248.072185(6)	333.5(28) d	α (99.99%)	²⁴⁴Cm	0+
²⁴⁸Cf	98	150	248.072185(6)	333.5(28) d	SF (.0029%)	(various)	0+
²⁴⁹Cf	98	151	249.0748535(24)	351(2) y	α	²⁴⁵Cm	9/2−
²⁴⁹Cf	98	151	249.0748535(24)	351(2) y	SF (5×10⁻⁷%)	(various)	9/2−
^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+
²⁵⁰Cf	98	152	250.0764061(22)	13.08(9) y	SF (.077%)	(various)	0+
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+
²⁵²Cf^{[n 9]}	98	154	252.081626(5)	2.645(8) y	SF (3.09%)^{[n 10]}	(various)	0+
²⁵³Cf	98	155	253.085133(7)	17.81(8) d	β⁻ (99.69%)	²⁵³Es	(7/2+)
²⁵³Cf	98	155	253.085133(7)	17.81(8) d	α (.31%)	²⁴⁹Cm	(7/2+)
²⁵⁴Cf	98	156	254.087323(13)	60.5(2) d	SF (99.69%)	(various)	0+
²⁵⁴Cf	98	156	254.087323(13)	60.5(2) d	α (.31%)	²⁵⁰Cm	0+
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	(various)	0+
This table header & footer: view

^ ^mCf – 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 the 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 v t e
Actinides^[12] by decay chain				Half-life range (a)	Fission products of ²³⁵U by yield^[13]
4n	4n + 1	4n + 2	4n + 3	Half-life range (a)	4.5–7%	0.04–1.25%	<0.001%
²²⁸Ra^№				4–6 a		¹⁵⁵Eu^þ
²⁴⁸Bk^[14]				> 9 a
²⁴⁴Cm^ƒ	²⁴¹Pu^ƒ	²⁵⁰Cf	²²⁷Ac^№	10–29 a	⁹⁰Sr	⁸⁵Kr	^113mCd^þ
²³²U^ƒ		²³⁸Pu^ƒ	²⁴³Cm^ƒ	29–97 a	¹³⁷Cs	¹⁵¹Sm^þ	^121mSn
	²⁴⁹Cf^ƒ	^242mAm^ƒ		141–351 a	No fission products have a half-life in the range of 100 a–210 ka ...
	²⁴¹Am^ƒ		²⁵¹Cf^ƒ^[15]	430–900 a
		²²⁶Ra^№	²⁴⁷Bk	1.3–1.6 ka
²⁴⁰Pu	²²⁹Th	²⁴⁶Cm^ƒ	²⁴³Am^ƒ	4.7–7.4 ka
	²⁴⁵Cm^ƒ	²⁵⁰Cm		8.3–8.5 ka
			²³⁹Pu^ƒ	24.1 ka
		²³⁰Th^№	²³¹Pa^№	32–76 ka
²³⁶Np^ƒ	²³³U^ƒ	²³⁴U^№		150–250 ka	⁹⁹Tc^₡	¹²⁶Sn
²⁴⁸Cm		²⁴²Pu		327–375 ka		⁷⁹Se^₡
				1.33 Ma	¹³⁵Cs^₡
	²³⁷Np^ƒ			1.61–6.5 Ma	⁹³Zr	¹⁰⁷Pd
²³⁶U			²⁴⁷Cm^ƒ	15–24 Ma		¹²⁹I^₡
²⁴⁴Pu				80 Ma	... nor beyond 15.7 Ma^[16]
²³²Th^№		²³⁸U^№	²³⁵U^ƒ№	0.7–14.1 Ga	... nor beyond 15.7 Ma^[16]
₡, 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 (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.^[17]

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).^[18]^[19]

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.^[20]

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.^[21]

References

^ CRC 2006, p. 11.196.
^ Sonzogni, Alejandro A. (Database Manager), ed. (2008). "Chart of Nuclides". National Nuclear Data Center, Brookhaven National Laboratory. Retrieved 1 March 2010.
^ 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.
^ 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.
^ 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.
^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (1 March 2021). "The NUBASE2020 evaluation of nuclear physics properties *". Chinese Physics C, High Energy Physics and Nuclear Physics. 45 (3): 030001. Bibcode:2021ChPhC..45c0001K. doi:10.1088/1674-1137/abddae. ISSN 1674-1137. OSTI 1774641. S2CID 233794940.
^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (1 March 2021). "The NUBASE2020 evaluation of nuclear physics properties *". Chinese Physics C, High Energy Physics and Nuclear Physics. 45 (3): 030001. Bibcode:2021ChPhC..45c0001K. doi:10.1088/1674-1137/abddae. ISSN 1674-1137. OSTI 1774641. S2CID 233794940.
^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (1 March 2021). "The NUBASE2020 evaluation of nuclear physics properties *". Chinese Physics C, High Energy Physics and Nuclear Physics. 45 (3): 030001. Bibcode:2021ChPhC..45c0001K. doi:10.1088/1674-1137/abddae. ISSN 1674-1137. OSTI 1774641. S2CID 233794940.
^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (1 March 2021). "The NUBASE2020 evaluation of nuclear physics properties *". Chinese Physics C, High Energy Physics and Nuclear Physics. 45 (3): 030001. Bibcode:2021ChPhC..45c0001K. doi:10.1088/1674-1137/abddae. ISSN 1674-1137. OSTI 1774641. S2CID 233794940.
^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (1 March 2021). "The NUBASE2020 evaluation of nuclear physics properties *". Chinese Physics C, High Energy Physics and Nuclear Physics. 45 (3): 030001. Bibcode:2021ChPhC..45c0001K. doi:10.1088/1674-1137/abddae. ISSN 1674-1137. OSTI 1774641. S2CID 233794940.
^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (1 March 2021). "The NUBASE2020 evaluation of nuclear physics properties *". Chinese Physics C, High Energy Physics and Nuclear Physics. 45 (3): 030001. Bibcode:2021ChPhC..45c0001K. doi:10.1088/1674-1137/abddae. ISSN 1674-1137. OSTI 1774641. S2CID 233794940.
^ 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.
^ Specifically from thermal neutron fission of uranium-235, e.g. in a typical nuclear reactor.
^ 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]."
^ This is the heaviest nuclide with a half-life of at least four years before the "sea of instability".
^ 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.
^ 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.
^ "Portable Isotopic Neutron Spectroscopy (PINS) for the Military". Frontier Technology Corp. Archived from the original on 2018-06-16. Retrieved 2016-02-24.
^ 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.
^ "Californium-252 & Antimony-Beryllium Sources". Frontier Technology Corp. Retrieved 2016-02-24.
^ 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.

Isotope masses from:
- Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
Isotopic compositions and standard atomic masses from:
- de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
- Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051.
"News & Notices: Standard Atomic Weights Revised". International Union of Pure and Applied Chemistry. 19 October 2005.
Half-life, spin, and isomer data selected from the following sources.
- Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
- National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
- Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.

[3] Cf – Excited nuclear isomer.

[4] ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.

[TMS-5] # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).

[6] Modes of decay:

EC: Electron capture

SF: Spontaneous fission

[7] ( ) spin value – Indicates spin with weak assignment arguments.

[TNN-8] # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).

[10] Lightest nuclide known to undergo spontaneous fission as the main decay mode

[19] High neutron cross-section, tends to absorb neutrons

[20] Most common isotope

[21] High neutron emitter, average 3.7 neutrons per fission

[FOOTNOTECRC200611.196-1] CRC 2006, p. 11.196.

[NNDC2008-2] Sonzogni, Alejandro A. (Database Manager), ed. (2008). "Chart of Nuclides". National Nuclear Data Center, Brookhaven National Laboratory. Retrieved 1 March 2010.

[9] 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.

[11] 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.

[12] 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.

[13] Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (1 March 2021). "The NUBASE2020 evaluation of nuclear physics properties *". Chinese Physics C, High Energy Physics and Nuclear Physics. 45 (3): 030001. Bibcode:2021ChPhC..45c0001K. doi:10.1088/1674-1137/abddae. ISSN 1674-1137. OSTI 1774641. S2CID 233794940.

[14] Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (1 March 2021). "The NUBASE2020 evaluation of nuclear physics properties *". Chinese Physics C, High Energy Physics and Nuclear Physics. 45 (3): 030001. Bibcode:2021ChPhC..45c0001K. doi:10.1088/1674-1137/abddae. ISSN 1674-1137. OSTI 1774641. S2CID 233794940.

[15] Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (1 March 2021). "The NUBASE2020 evaluation of nuclear physics properties *". Chinese Physics C, High Energy Physics and Nuclear Physics. 45 (3): 030001. Bibcode:2021ChPhC..45c0001K. doi:10.1088/1674-1137/abddae. ISSN 1674-1137. OSTI 1774641. S2CID 233794940.

[16] Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (1 March 2021). "The NUBASE2020 evaluation of nuclear physics properties *". Chinese Physics C, High Energy Physics and Nuclear Physics. 45 (3): 030001. Bibcode:2021ChPhC..45c0001K. doi:10.1088/1674-1137/abddae. ISSN 1674-1137. OSTI 1774641. S2CID 233794940.

[17] Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (1 March 2021). "The NUBASE2020 evaluation of nuclear physics properties *". Chinese Physics C, High Energy Physics and Nuclear Physics. 45 (3): 030001. Bibcode:2021ChPhC..45c0001K. doi:10.1088/1674-1137/abddae. ISSN 1674-1137. OSTI 1774641. S2CID 233794940.

[18] Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (1 March 2021). "The NUBASE2020 evaluation of nuclear physics properties *". Chinese Physics C, High Energy Physics and Nuclear Physics. 45 (3): 030001. Bibcode:2021ChPhC..45c0001K. doi:10.1088/1674-1137/abddae. ISSN 1674-1137. OSTI 1774641. S2CID 233794940.

[22] 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.

[23] Specifically from thermal neutron fission of uranium-235, e.g. in a typical nuclear reactor.

[24] 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]."

[25] This is the heaviest nuclide with a half-life of at least four years before the "sea of instability".

[26] 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.

[252Cf-Dicello-27] 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.

[252Cf-frontier-cf252-28] "Portable Isotopic Neutron Spectroscopy (PINS) for the Military". Frontier Technology Corp. Archived from the original on 2018-06-16. Retrieved 2016-02-24.

[252Cf-Martin-29] 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.

[252Cf-frontier-cf252b-30] "Californium-252 & Antimony-Beryllium Sources". Frontier Technology Corp. Retrieved 2016-02-24.

[252Cf-Maruyama-31] 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.

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@@ Line 51: / Line 51: @@
 | <sup>239</sup>Bk
 |-
-| rowspan=3|<sup>240</sup>Cf<ref>{{cite journal |last1=Kondev |first1=F. G. |last2=Wang |first2=M. |last3=Huang |first3=W. J. |last4=Naimi |first4=S. |last5=Audi |first5=G. |title=The NUBASE2020 evaluation of nuclear physics properties * |journal=Chinese Physics C, High Energy Physics and Nuclear Physics |date=1 March 2021 |volume=45 |issue=3 |page=030001 |doi=10.1088/1674-1137/abddae |bibcode=2021ChPhC..45c0001K |osti=1774641 |s2cid=233794940 |url=https://www.osti.gov/biblio/1774641 |access-date=24 June 2023 |language=English |issn=1674-1137|doi-access=free }}</ref>
+| rowspan=3|<sup>240</sup>Cf<ref>{{cite journal |last1=Kondev |first1=F. G. |last2=Wang |first2=M. |last3=Huang |first3=W. J. |last4=Naimi |first4=S. |last5=Audi |first5=G. |title=The NUBASE2020 evaluation of nuclear physics properties * |journal=Chinese Physics C, High Energy Physics and Nuclear Physics |date=1 March 2021 |volume=45 |issue=3 |page=030001 |doi=10.1088/1674-1137/abddae |bibcode=2021ChPhC..45c0001K |osti=1774641 |s2cid=233794940 |language=English |issn=1674-1137|doi-access=free }}</ref>
 | rowspan=3 style="text-align:right" | 98
 | rowspan=3 style="text-align:right" | 142
@@ Line 66: / Line 66: @@
 | <sup>240</sup>Bk
 |-
-| rowspan=2|<sup>241</sup>Cf<ref>{{cite journal |last1=Kondev |first1=F. G. |last2=Wang |first2=M. |last3=Huang |first3=W. J. |last4=Naimi |first4=S. |last5=Audi |first5=G. |title=The NUBASE2020 evaluation of nuclear physics properties * |journal=Chinese Physics C, High Energy Physics and Nuclear Physics |date=1 March 2021 |volume=45 |issue=3 |page=030001 |doi=10.1088/1674-1137/abddae |bibcode=2021ChPhC..45c0001K |osti=1774641 |s2cid=233794940 |url=https://www.osti.gov/biblio/1774641 |access-date=24 June 2023 |language=English |issn=1674-1137|doi-access=free }}</ref>
+| rowspan=2|<sup>241</sup>Cf<ref>{{cite journal |last1=Kondev |first1=F. G. |last2=Wang |first2=M. |last3=Huang |first3=W. J. |last4=Naimi |first4=S. |last5=Audi |first5=G. |title=The NUBASE2020 evaluation of nuclear physics properties * |journal=Chinese Physics C, High Energy Physics and Nuclear Physics |date=1 March 2021 |volume=45 |issue=3 |page=030001 |doi=10.1088/1674-1137/abddae |bibcode=2021ChPhC..45c0001K |osti=1774641 |s2cid=233794940 |language=English |issn=1674-1137|doi-access=free }}</ref>
 | rowspan=2 style="text-align:right" | 98
 | rowspan=2 style="text-align:right" | 143
@@ Line 78: / Line 78: @@
 | <sup>237</sup>Cm
 |-
-| rowspan=3|<sup>242</sup>Cf<ref>{{cite journal |last1=Kondev |first1=F. G. |last2=Wang |first2=M. |last3=Huang |first3=W. J. |last4=Naimi |first4=S. |last5=Audi |first5=G. |title=The NUBASE2020 evaluation of nuclear physics properties * |journal=Chinese Physics C, High Energy Physics and Nuclear Physics |date=1 March 2021 |volume=45 |issue=3 |page=030001 |doi=10.1088/1674-1137/abddae |bibcode=2021ChPhC..45c0001K |osti=1774641 |s2cid=233794940 |url=https://www.osti.gov/biblio/1774641 |access-date=24 June 2023 |language=English |issn=1674-1137|doi-access=free }}</ref>
+| rowspan=3|<sup>242</sup>Cf<ref>{{cite journal |last1=Kondev |first1=F. G. |last2=Wang |first2=M. |last3=Huang |first3=W. J. |last4=Naimi |first4=S. |last5=Audi |first5=G. |title=The NUBASE2020 evaluation of nuclear physics properties * |journal=Chinese Physics C, High Energy Physics and Nuclear Physics |date=1 March 2021 |volume=45 |issue=3 |page=030001 |doi=10.1088/1674-1137/abddae |bibcode=2021ChPhC..45c0001K |osti=1774641 |s2cid=233794940 |language=English |issn=1674-1137|doi-access=free }}</ref>
 | rowspan=3 style="text-align:right" | 98
 | rowspan=3 style="text-align:right" | 144
@@ Line 93: / Line 93: @@
 | (various)
 |-
-| rowspan=2|<sup>243</sup>Cf<ref>{{cite journal |last1=Kondev |first1=F. G. |last2=Wang |first2=M. |last3=Huang |first3=W. J. |last4=Naimi |first4=S. |last5=Audi |first5=G. |title=The NUBASE2020 evaluation of nuclear physics properties * |journal=Chinese Physics C, High Energy Physics and Nuclear Physics |date=1 March 2021 |volume=45 |issue=3 |page=030001 |doi=10.1088/1674-1137/abddae |bibcode=2021ChPhC..45c0001K |osti=1774641 |s2cid=233794940 |url=https://www.osti.gov/biblio/1774641 |access-date=24 June 2023 |language=English |issn=1674-1137|doi-access=free }}</ref>
+| rowspan=2|<sup>243</sup>Cf<ref>{{cite journal |last1=Kondev |first1=F. G. |last2=Wang |first2=M. |last3=Huang |first3=W. J. |last4=Naimi |first4=S. |last5=Audi |first5=G. |title=The NUBASE2020 evaluation of nuclear physics properties * |journal=Chinese Physics C, High Energy Physics and Nuclear Physics |date=1 March 2021 |volume=45 |issue=3 |page=030001 |doi=10.1088/1674-1137/abddae |bibcode=2021ChPhC..45c0001K |osti=1774641 |s2cid=233794940 |language=English |issn=1674-1137|doi-access=free }}</ref>
 | rowspan=2 style="text-align:right" | 98
 | rowspan=2 style="text-align:right" | 145
@@ Line 105: / Line 105: @@
 | <sup>239</sup>Cm
 |-
-| rowspan=2|<sup>244</sup>Cf<ref>{{cite journal |last1=Kondev |first1=F. G. |last2=Wang |first2=M. |last3=Huang |first3=W. J. |last4=Naimi |first4=S. |last5=Audi |first5=G. |title=The NUBASE2020 evaluation of nuclear physics properties * |journal=Chinese Physics C, High Energy Physics and Nuclear Physics |date=1 March 2021 |volume=45 |issue=3 |page=030001 |doi=10.1088/1674-1137/abddae |bibcode=2021ChPhC..45c0001K |osti=1774641 |s2cid=233794940 |url=https://www.osti.gov/biblio/1774641 |access-date=24 June 2023 |language=English |issn=1674-1137|doi-access=free }}</ref>
+| rowspan=2|<sup>244</sup>Cf<ref>{{cite journal |last1=Kondev |first1=F. G. |last2=Wang |first2=M. |last3=Huang |first3=W. J. |last4=Naimi |first4=S. |last5=Audi |first5=G. |title=The NUBASE2020 evaluation of nuclear physics properties * |journal=Chinese Physics C, High Energy Physics and Nuclear Physics |date=1 March 2021 |volume=45 |issue=3 |page=030001 |doi=10.1088/1674-1137/abddae |bibcode=2021ChPhC..45c0001K |osti=1774641 |s2cid=233794940 |language=English |issn=1674-1137|doi-access=free }}</ref>
 | rowspan=2 style="text-align:right" | 98
 | rowspan=2 style="text-align:right" | 146
@@ Line 117: / Line 117: @@
 | <sup>244</sup>Bk
 |-
-| rowspan=2|<sup>245</sup>Cf<ref>{{cite journal |last1=Kondev |first1=F. G. |last2=Wang |first2=M. |last3=Huang |first3=W. J. |last4=Naimi |first4=S. |last5=Audi |first5=G. |title=The NUBASE2020 evaluation of nuclear physics properties * |journal=Chinese Physics C, High Energy Physics and Nuclear Physics |date=1 March 2021 |volume=45 |issue=3 |page=030001 |doi=10.1088/1674-1137/abddae |bibcode=2021ChPhC..45c0001K |osti=1774641 |s2cid=233794940 |url=https://www.osti.gov/biblio/1774641 |access-date=24 June 2023 |language=English |issn=1674-1137|doi-access=free }}</ref>
+| rowspan=2|<sup>245</sup>Cf<ref>{{cite journal |last1=Kondev |first1=F. G. |last2=Wang |first2=M. |last3=Huang |first3=W. J. |last4=Naimi |first4=S. |last5=Audi |first5=G. |title=The NUBASE2020 evaluation of nuclear physics properties * |journal=Chinese Physics C, High Energy Physics and Nuclear Physics |date=1 March 2021 |volume=45 |issue=3 |page=030001 |doi=10.1088/1674-1137/abddae |bibcode=2021ChPhC..45c0001K |osti=1774641 |s2cid=233794940 |language=English |issn=1674-1137|doi-access=free }}</ref>
 | rowspan=2 style="text-align:right" | 98
 | rowspan=2 style="text-align:right" | 147