Isotopes of berkelium

Isotopes of berkelium (₉₇Bk)

Main isotopes[1] Decay abun­dance half-life (t1/2) mode pro­duct ^245Bk synth 4.94 d ε ^245Cm α ^241Am ^246Bk synth 1.8 d α ^242Am β^+ ^246Cm ^247Bk synth 1380 y α ^243Am ^248Bk synth >9 y[2] α ^244Am ^249Bk synth 330 d β^− ^249Cf α ^245Am SF –

Berkelium (₉₇Bk) 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 ²⁴³Bk in 1949. There are twenty known radioisotopes, from ²³³Bk and ²³³Bk to ²⁵³Bk (except ²³⁵Bk and ²³⁷Bk), and six nuclear isomers. The longest-lived isotope is ²⁴⁷Bk with a half-life of 1,380 years.

List of isotopes

Nuclide [n 1]	Z	N	Isotopic mass (Da)[3] [n 2][n 3]	Half-life[1]	Decay mode[1] [n 4]	Daughter isotope	Spin and parity[1] [n 5][n 6]
	Excitation energy[n 6]
^233Bk	97	136	233.05665(25)#	40(30) s	α	^229Am	3/2-#
					β^+?	^233Cm
^234Bk	97	137	234.05732(16)#	20(5) s	α (>80%)	^230Am	3-#
					β^+ (<20%)	^234Cm
					β^+, SF?[4]	(various)
^236Bk	97	139	236.05748(39)#	26(10) s	β^+ (99.96%)	^236Cm	4+#
					β^+, SF (0.04%)	(various)
					α?	^232Am
^238Bk	97	141	238.05820(28)#	2.40(8) min	β^+ (99.95%)	^238Cm	1#
					β^+, SF (0.048%)	(various)
					α?	^234Am
^239Bk	97	142	239.05824(22)#	100# s	β^+	^239Cm	(7/2+)
					α?	^235Am
					SF?	(various)
^240Bk	97	143	240.05976(16)#	4.8(8) min	β^+?	^240Cm	7−#
					β^+, SF (0.0020%)	(various)
					α?	^236Am
^241Bk	97	144	241.06010(18)#	4.6(4) min	β^+?	^241Cm	(7/2+)
					α?	^237Am
^242Bk	97	145	242.06198(22)#	7.0(13) min	β^+	^242Cm	3+#
					β^+, SF (<3×10^−5%)	(various)
					α?	^238Am
^242mBk	2000(200)# keV			600(100) ns	SF	(various)
					IT?	^242Bk
^243Bk	97	146	243.0630059(49)	4.6(2) h	β^+ (99.85%)	^243Cm	3/2−
					α (.15%)	^239Am
^244Bk	97	147	244.065179(15)	5.02(3) h	β^+?	^244Cm	4−
					α (0.006%)	^240Am
^244mBk	1500(500)# keV			820(60) ns	SF	(various)
					IT?	^244Bk
^245Bk	97	148	245.0663598(19)	4.95(3) d	EC (99.88%)	^245Cm	3/2−
					α (.12%)	^241Am
^246Bk	97	149	246.068671(64)	1.80(2) d	β^+	^246Cm	2(−)
					α?	^242Am
^247Bk	97	150	247.0703059(56)	1.38(25)×10^3 y	α	^243Am	3/2−
					SF?	(various)
^248Bk	97	151	248.073142(54)	>9 y	α?	^244Am	6+#
					EC?	^248Cm
^248mBk[n 7]	−20(50) keV			23.7(2) h	β^− (70%)	^248Cf	1(−)
					EC (30%)	^248Cm
					α?	^244Am
^249Bk	97	152	249.0749831(13)	327.2(3) d	β^−	^249Cf	7/2+
					α (.00145%)	^245Am
					SF (4.7×10^−8%)	(various)
^249mBk	8.777(14) keV			300 μs	IT	^249Bk	3/2−
^250Bk	97	153	250.0783172(31)	3.212(5) h	β^−	^250Cf	2−
^250m1Bk	35.59(10) keV			29(1) μs	IT	^250Bk	4+
^250m2Bk	85.6(16) keV			213(8) μs	IT	^250Bk	7+
^251Bk	97	154	251.080761(12)	55.6(11) min	β^−	^251Cf	(3/2−)
^251mBk	35.5(13) keV			58(4) μs	IT	^251Bk	(7/2+)
^252Bk	97	155	252.08431(22)#	1.8(5) min	β^−?	^252Cf
					α?	^248Am
^253Bk	97	156	253.08688(39)#	60# min	β^−?	^253Cf	3/2-#
This table header & footer: view

1. ^mBk – 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. Order of ground state and isomer is uncertain.

Actinides vs fission products

Actinides and fission products by half-life v t e
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%
^228Ra^№				4–6 a		^155Eu^þ
^248Bk[7]				> 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[8]	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[9]
^232Th^№		^238U^№	^235U^ƒ№	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)

References

1. 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.
2. 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. doi:10.1016/0029-5582(65)90719-4.
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. Kaji, D.; Morimoto, K.; Haba, H.; Ideguchi, E.; Koura, H.; Morita, K. (2016). "Decay Properties of New Isotopes ²³⁴Bk and ²³⁰Am, and Even–Even Nuclides ²³⁴Cm and ²³⁰Pu" (PDF). Journal of the Physical Society of Japan. 84 (15002): 015002. Bibcode:2016JPSJ...85a5002K. doi:10.7566/JPSJ.85.015002.
5. 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.
6. Specifically from thermal neutron fission of uranium-235, e.g. in a typical nuclear reactor.
7. 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]."
8. This is the heaviest nuclide with a half-life of at least four years before the "sea of instability".
9. 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.

• 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
• 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.