Isotopes of berkelium

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 18 known radioisotopes, from ²³³Bk to ²⁵³Bk (with the exception of ²³⁵Bk, ²³⁷Bk, and ²³⁹Bk), and 6 nuclear isomers. The longest-lived isotope is ²⁴⁷Bk with a half-life of 1,380 years.

Main isotopes of berkelium (₉₇Bk)

Iso­tope Decay abun­dance half-life (t1/2) mode pro­duct ^245Bk syn 4.94 d ε ^245Cm α ^241Am ^246Bk syn 1.8 d α ^242Am ε ^246Cm ^247Bk syn 1380 y α ^243Am ^248Bk syn >300 y[1] α ^244Am ^249Bk syn 330 d α ^245Am SF – β^− ^249Cf

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]
	Excitation energy[n 6]
^233Bk[2]	97	136		21 s	α	^229Am
^234Bk[3]	97	137		19(+6-4) s	α (50%)	^230Am
					β^+ (50%)	^234Cm
^236Bk	97	139	236.05733(43)#	22(+13-6) s[4]	α	^232Am
					β^+	^236Cm
^238Bk	97	141	238.05828(31)#	2.40(8) min	α	^234Am
					β^+, SF (.048%)	(various)
					β^+ (rare)	^238Cm
^240Bk	97	143	240.05976(16)#	4.8(8) min	β^+ (90%)	^240Cm
					α (10%)	^236Am
					β^+, SF (.002%)	(various)
^241Bk	97	144	241.06023(22)#	4.6(4) min	α	^237Am	(7/2+)
					β^+ (rare)	^241Cm
^242Bk	97	145	242.06198(22)#	7.0(13) min	β^+ (99.99%)	^242Cm	2−#
					β^+, SF (3×10^−4%)	(various)
^242mBk	200(200)# keV			600(100) ns	SF	(various)
^243Bk	97	146	243.063008(5)	4.5(2) h	β^+ (99.85%)	^243Cm	(3/2−)
					α (.15%)	^239Am
^244Bk	97	147	244.065181(16)	4.35(15) h	β^+ (99.99%)	^244Cm	(4−)#
					α (.006%)	^240Am
^245Bk	97	148	245.0663616(25)	4.94(3) d	EC (99.88%)	^245Cm	3/2−
					α (.12%)	^241Am
^246Bk	97	149	246.06867(6)	1.80(2) d	β^+ (99.8%)	^246Cm	2(−)
					α (.2%)	^242Am
^247Bk	97	150	247.070307(6)	1.38(25)×10^3 y	α	^243Am	(3/2−)
					SF (rare)	(various)
^248Bk	97	151	248.07309(8)#	>300 y[5]	α	^244Am	6+#
^248mBk	30(70)# keV			23.7(2) h	β^−	^248Cf	1(−)
^249Bk[n 7]	97	152	249.0749867(28)	330(4) d	β^−	^249Cf	7/2+
					α (.00145%)	^245Am
					SF (4.7×10^−8%)	(various)
^249mBk	8.80(10) keV			300 µs	IT	^249Bk	(3/2−)
^250Bk	97	153	250.078317(4)	3.212(5) h	β^−	^250Cf	2−
^250m1Bk	35.59(5) keV			29(1) µs	IT	^250Bk	(4+)
^250m2Bk	84.1(21) keV			213(8) µs			(7+)
^251Bk	97	154	251.080760(12)	55.6(11) min	β^−	^251Cf	(3/2−)#
					α (10^−5%)	^247Am
^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)#	10# min	β^−	^253Cf

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. Easiest isotope to synthesize

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	†		^155Eu^þ
^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
^248Bk[8]	^249Cf^ƒ	^242mAm^ƒ		141–351 a	No fission products have a half-life in the range of 100–210 ka ...
	^241Am^ƒ		^251Cf^ƒ[9]	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^₡
				1.53 Ma		^93Zr
	^237Np^ƒ			2.1–6.5 Ma		^135Cs^₡	^107Pd
^236U			^247Cm^ƒ	15–24 Ma			^129I^₡
^244Pu				80 Ma	... nor beyond 15.7 Ma[10]
^232Th^№		^238U^№	^235U^ƒ№	0.7–14.1 Ga
Legend for superscript symbols ₡  has thermal neutron capture cross section in the range of 8–50 barns ƒ  fissile m  metastable isomer №  primarily a naturally occurring radioactive material (NORM) þ  neutron poison (thermal neutron capture cross section greater than 3k barns) †  range 4–97 a: Medium-lived fission product ‡  over 200 ka: Long-lived fission product

See also

References

1. 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.
2. "Observation of new neutron-deficient isotopes with Z ≥ 92 in multinucleon transfer reactions" http://inspirehep.net/record/1383747/files/scoap3-fulltext.pdf
3. 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. doi:10.7566/JPSJ.85.015002.
4. Konki, J.; et al. (10 Jan 2017). "Towards saturation of the electron-capture delayed fission probability: The new isotopes ²⁴⁰Es and ²³⁶Bk". Physics Letters B. 764: 265–270. Bibcode:2017PhLB..764..265K. doi:10.1016/j.physletb.2016.11.038. ISSN 0370-2693.
5. 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.
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 U-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.

• 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. Lay summary.
• 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.