Isotopes of fermium

Isotopes of fermium (₁₀₀Fm)
α	248Cf
α	249Cf
α	251Cf
SF	–

Fermium (₁₀₀Fm) is a synthetic element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be discovered (in fallout from nuclear testing) was ²⁵⁵Fm in 1952. ²⁵⁰Fm was independently synthesized shortly after the discovery of ²⁵⁵Fm. There are 20 known radioisotopes ranging in atomic mass from ²⁴¹Fm to ²⁶⁰Fm (²⁶⁰Fm is unconfirmed), and 4 nuclear isomers, ^247mFm, ^250mFm, ^251mFm, and ^253mFm. The longest-lived isotope is ²⁵⁷Fm with a half-life of 100.5 days, and the longest-lived isomer is ^247mFm with a half-life of 5.1 seconds.

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]
²⁴¹Fm	100	141	241.07421(32)#	730(60) μs	SF	(various)	5/2+#
²⁴¹Fm	100	141	241.07421(32)#	730(60) μs	α (<14%)	²³⁷Cf	5/2+#
²⁴²Fm	100	142	242.07343(43)#	<4 μs[2]	SF	(various)	0+
²⁴³Fm[3]	100	143	243.07447(23)#	231(9) ms	α (91%)	²³⁹Cf	(7/2−)
					SF (9%)	(various)
					β⁺ (<10%)	²⁴³Es
²⁴⁴Fm[2]	100	144	244.07404(22)#	3.12(8) ms	SF	(various)	0+
²⁴⁴Fm[2]	100	144	244.07404(22)#	3.12(8) ms	α (<1%)	²⁴⁰Cf	0+
²⁴⁵Fm[4]	100	145	245.07535(21)#	5.5(7) s	α (88.5%)	²⁴¹Cf	(1/2+)
					β⁺ (11.5%)	²⁴⁵Es
					SF (<0.3%)[3]	(various)
²⁴⁶Fm[5]	100	146	246.075350(17)	1.54(4) s	α (93.2%)	²⁴²Cf	0+
					SF (6.8%)	(various)
					β⁺ (<1.3%)	²⁴⁶Es
²⁴⁷Fm[6]	100	147	247.07695(12)#	31(1) s	α (64%)	²⁴³Cf	(7/2+)
²⁴⁷Fm[6]	100	147	247.07695(12)#	31(1) s	β⁺ (36%)	²⁴⁷Es	(7/2+)
^247mFm	45(7) keV			5.1(2) s	α (88%)	²⁴³Cf	(1/2+)
					IT (12%)	²⁴⁷Fm
					β⁺?	²⁴⁷Es
²⁴⁸Fm	100	148	248.077186(9)	35.1(8) s	α (93%)	²⁴⁴Cf	0+
					β⁺ (7%)	²⁴⁸Es
					SF (.10%)	(various)
²⁴⁹Fm	100	149	249.078928(7)	1.6(1) min	β⁺ (84.4%)	²⁴⁹Es	(7/2+)
²⁴⁹Fm	100	149	249.078928(7)	1.6(1) min	α (15.6%)[7]	²⁴⁵Cf	(7/2+)
²⁵⁰Fm	100	150	250.079521(9)	30.4(15) min	α (90%)	²⁴⁶Cf	0+
					EC (10%)	²⁵⁰Es
					SF (6.9×10⁻³%)	(various)
^250mFm	1199.2(10) keV			1.92(5) s	IT	²⁵⁰Fm	(8−)
²⁵¹Fm	100	151	251.081540(16)	5.30(8) h	β⁺ (98.2%)	²⁵¹Es	(9/2−)
²⁵¹Fm	100	151	251.081540(16)	5.30(8) h	α (1.8%)	²⁴⁷Cf	(9/2−)
^251mFm	200.09(11) keV			21.1(16) μs	IT	²⁵¹Fm	(5/2+)
²⁵²Fm	100	152	252.082467(6)	25.39(4) h	α (99.99%)	²⁴⁸Cf	0+
²⁵²Fm	100	152	252.082467(6)	25.39(4) h	SF (.0023%)	(various)	0+
²⁵³Fm	100	153	253.085185(4)	3.00(12) d	EC (88%)	²⁵³Es	(1/2)+
²⁵³Fm	100	153	253.085185(4)	3.00(12) d	α (12%)	²⁴⁹Cf	(1/2)+
^253mFm[8]	~351 keV			0.56(6) μs	IT	²⁵³Fm	(11/2-)
²⁵⁴Fm	100	154	254.0868544(30)	3.240(2) h	α (99.94%)	²⁵⁰Cf	0+
²⁵⁴Fm	100	154	254.0868544(30)	3.240(2) h	SF (.0592%)	(various)	0+
²⁵⁵Fm	100	155	255.089964(5)	20.07(7) h	α	²⁵¹Cf	7/2+
²⁵⁵Fm	100	155	255.089964(5)	20.07(7) h	SF (2.4×10⁻⁵%)	(various)	7/2+
²⁵⁶Fm	100	156	256.091774(8)	157.6(13) min	SF (91.9%)	(various)	0+
²⁵⁶Fm	100	156	256.091774(8)	157.6(13) min	α (8.1%)	²⁵²Cf	0+
²⁵⁷Fm[n 7]	100	157	257.095106(7)	100.5(2) d	α (99.79%)	²⁵³Cf	(9/2+)
²⁵⁷Fm[n 7]	100	157	257.095106(7)	100.5(2) d	SF (.21%)	(various)	(9/2+)
²⁵⁸Fm	100	158	258.09708(22)#	370(14) μs	SF	(various)	0+
²⁵⁹Fm	100	159	259.1006(3)#	1.5(3) s	SF	(various)	3/2+#
²⁶⁰Fm[n 8][n 9]	100	160	260.10281(55)#	4 ms	SF	(various)	0+
This table header & footer:

^mFm – 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

IT: Isomeric transition

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).
Heaviest nuclide produced via neutron capture
Discovery of this isotope is unconfirmed
Not directly synthesized, occurs as decay product of ²⁶⁰Md

Chronology of isotope discovery

Isotope	Discovered	Reaction
²⁴¹Fm	2008	²⁰⁴Pb(⁴⁰Ar,3n)
²⁴²Fm	1975	²⁰⁴Pb(⁴⁰Ar,2n), ²⁰⁶Pb(⁴⁰Ar,4n)
²⁴³Fm	1981	²⁰⁶Pb(⁴⁰Ar,3n)
²⁴⁴Fm	1967	²³³U(¹⁶O,5n)
²⁴⁵Fm	1967	²³³U(¹⁶O,4n)
²⁴⁶Fm	1966	²³⁵U(¹⁶O,5n)
²⁴⁷Fm	1967	²³⁹Pu(¹²C,4n)
²⁴⁸Fm	1958	²⁴⁰Pu(¹²C,4n)
²⁴⁹Fm	1960	²³⁸U(¹⁶O,5n)
²⁵⁰Fm	1954	²³⁸U(¹⁶O,4n)
²⁵¹Fm	1957	²⁴⁹Cf(α,2n)
²⁵²Fm	1956	²⁴⁹Cf(α,n)
²⁵³Fm	1957	²⁵²Cf(α,3n)
²⁵⁴Fm	1954	Neutron capture
²⁵⁵Fm	1954	Neutron capture
²⁵⁶Fm	1955	Neutron capture
²⁵⁷Fm	1964	Neutron capture
²⁵⁸Fm	1971	²⁵⁷Fm(d,p)
²⁵⁹Fm	1980	²⁵⁷Fm(t,p)
²⁶⁰Fm?	1992?	²⁵⁴Es+¹⁸O, ²²Ne — transfer (EC of ²⁶⁰Md)

²⁶⁰Fm was not confirmed in 1997.

References

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.
Khuyagbaatar, J.; Hofmann, S.; Heßberger, F. P.; Ackermann, D.; Burkhard, H. G.; Heinz, S.; Kindler, B.; Kojouharov, I.; Lommel, B.; Mann, R.; Maurer, J.; Nishio, K.; Novikov, Yu. (1 August 2008). "Spontaneous fission of neutron-deficient fermium isotopes and the new nucleus 241Fm" (PDF). The European Physical Journal A. 37 (2): 177–183. Bibcode:2008EPJA...37..177K. doi:10.1140/epja/i2008-10608-4. ISSN 1434-601X. S2CID 18977014. Retrieved 24 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.
Tezekbayeva, M. S.; Yeremin, A. V.; Svirikhin, A. I.; Lopez-Martens, A.; Chelnokov, M. L.; Chepigin, V. I.; Isaev, A. V.; Izosimov, I. N.; Karpov, A. V.; Kuznetsova, A. A.; Malyshev, O. N.; Mukhin, R. S.; Popeko, A. G.; Popov, Yu. A.; Rachkov, V. A.; Sailaubekov, B. S.; Sokol, E. A.; Hauschild, K.; Jacob, H.; Chakma, R.; Dorvaux, O.; Forge, M.; Gall, B.; Kessaci, K.; Andel, B.; Antalic, S.; Bronis, A.; Mosat, P. (24 March 2022). "Study of the production and decay properties of neutron-deficient nobelium isotopes". The European Physical Journal A. 58 (3): 52. arXiv:2203.15659. Bibcode:2022EPJA...58...52T. doi:10.1140/epja/s10050-022-00707-9. ISSN 1434-601X. S2CID 247720708. Retrieved 24 June 2023.
Venhart, M.; Heßberger, F. P.; Ackermann, D.; Antalic, S.; Gray-Jones, C.; Greenlees, P. T.; Heinz, S.; Herzberg, R. -D.; Hofmann, S.; Ketelhut, S.; Kindler, B.; Kojouharov, I.; Leino, M.; Lommel, B.; Mann, R.; Papadakis, P.; Rostron, D.; Rudolph, D.; Šáro, Š.; Sulignano, B. (4 February 2011). "Decay study of 246Fm at SHIP" (PDF). The European Physical Journal A. 47 (2): 20. Bibcode:2011EPJA...47...20V. doi:10.1140/epja/i2011-11020-9. ISSN 1434-601X. S2CID 119353521. Retrieved 24 June 2023.
Heßberger, F. P.; Hofmann, S.; Ackermann, D.; Antalic, S.; Kindler, B.; Kojouharov, I.; Kuusiniemi, P.; Leino, M.; Lommel, B.; Mann, R.; Nishio, K.; Popeko, A. G.; Sulignano, B.; Saro, S.; Streicher, B.; Venhart, M.; Yeremin, A. V. (1 December 2006). "Alpha-gamma decay studies of 255Rf, 251No and 247Fm" (PDF). The European Physical Journal A - Hadrons and Nuclei. 30 (3): 561–569. Bibcode:2006EPJA...30..561H. doi:10.1140/epja/i2006-10137-2. ISSN 1434-601X. S2CID 123871572. Retrieved 24 June 2023.
Heßberger, F. P.; Antalic, S.; Ackermann, D.; Kalaninová, Z.; Heinz, S.; Hofmann, S.; Streicher, B.; Kindler, B.; Kojouharov, I.; Kuusiniemi, P.; Leino, M.; Lommel, B.; Mann, R.; Nishio, K.; Šáro, Š.; Sulignano, B.; Venhart, M. (29 May 2012). "Alpha-gamma decay studies of 253No and its daughter products 253Md , 249Fm" (PDF). The European Physical Journal A. 48 (5): 75. Bibcode:2012EPJA...48...75H. doi:10.1140/epja/i2012-12075-8. ISSN 1434-601X. S2CID 254111959. Retrieved 25 June 2023.
Antalic, S.; Heßberger, F. P.; Ackermann, D.; Heinz, S.; Hofmann, S.; Kalaninová, Z.; Kindler, B.; Khuyagbaatar, J.; Kojouharov, I.; Kuusiniemi, P.; Leino, M.; Lommel, B.; Mann, R.; Nishio, K.; Šáro, Š.; Streicher, B.; Sulignano, B.; Venhart, M. (20 May 2011). "Isomeric states in 253No and 253Fm" (PDF). The European Physical Journal A. 47 (5): 62. Bibcode:2011EPJA...47...62A. doi:10.1140/epja/i2011-11062-y. ISSN 1434-601X. S2CID 121080273. Retrieved 25 June 2023.

Isotope masses from:
- M. Wang; G. Audi; A. H. Wapstra; F. G. Kondev; M. MacCormick; X. Xu; et al. (2012). "The AME2012 atomic mass evaluation (II). Tables, graphs and references" (PDF). Chinese Physics C. 36 (12): 1603–2014. Bibcode:2012ChPhC..36....3M. doi:10.1088/1674-1137/36/12/003. S2CID 250839471.
- 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.
- G. Audi; F. G. Kondev; M. Wang; B. Pfeiffer; X. Sun; J. Blachot; M. MacCormick (2012). "The NUBASE2012 evaluation of nuclear properties" (PDF). Chinese Physics C. 36 (12): 1157–1286. Bibcode:2012ChPhC..36....1A. doi:10.1088/1674-1137/36/12/001. Archived from the original (PDF) on 2014-02-22.
- 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.
- M. Thoennessen (2012). "Discovery of Isotopes of Elements with Z≥100". Atomic Data and Nuclear Data Tables. 99 (3): 312–344. arXiv:1203.2105. Bibcode:2013ADNDT..99..312T. doi:10.1016/j.adt.2012.03.003. S2CID 94982856.

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[2] Fm – Excited nuclear isomer.

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

[TMS-4] # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).

[5] Modes of decay:

EC: Electron capture

IT: Isomeric transition

SF: Spontaneous fission

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

[TNN-7] # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).

[15] Heaviest nuclide produced via neutron capture

[uc-16] Discovery of this isotope is unconfirmed

[17] Not directly synthesized, occurs as decay product of ²⁶⁰Md

[NUBASE2020-1] 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.

[:1-8] Khuyagbaatar, J.; Hofmann, S.; Heßberger, F. P.; Ackermann, D.; Burkhard, H. G.; Heinz, S.; Kindler, B.; Kojouharov, I.; Lommel, B.; Mann, R.; Maurer, J.; Nishio, K.; Novikov, Yu. (1 August 2008). "Spontaneous fission of neutron-deficient fermium isotopes and the new nucleus 241Fm" (PDF). The European Physical Journal A. 37 (2): 177–183. Bibcode:2008EPJA...37..177K. doi:10.1140/epja/i2008-10608-4. ISSN 1434-601X. S2CID 18977014. Retrieved 24 June 2023.

[:0-9] 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.

[10] Tezekbayeva, M. S.; Yeremin, A. V.; Svirikhin, A. I.; Lopez-Martens, A.; Chelnokov, M. L.; Chepigin, V. I.; Isaev, A. V.; Izosimov, I. N.; Karpov, A. V.; Kuznetsova, A. A.; Malyshev, O. N.; Mukhin, R. S.; Popeko, A. G.; Popov, Yu. A.; Rachkov, V. A.; Sailaubekov, B. S.; Sokol, E. A.; Hauschild, K.; Jacob, H.; Chakma, R.; Dorvaux, O.; Forge, M.; Gall, B.; Kessaci, K.; Andel, B.; Antalic, S.; Bronis, A.; Mosat, P. (24 March 2022). "Study of the production and decay properties of neutron-deficient nobelium isotopes". The European Physical Journal A. 58 (3): 52. arXiv:2203.15659. Bibcode:2022EPJA...58...52T. doi:10.1140/epja/s10050-022-00707-9. ISSN 1434-601X. S2CID 247720708. Retrieved 24 June 2023.

[11] Venhart, M.; Heßberger, F. P.; Ackermann, D.; Antalic, S.; Gray-Jones, C.; Greenlees, P. T.; Heinz, S.; Herzberg, R. -D.; Hofmann, S.; Ketelhut, S.; Kindler, B.; Kojouharov, I.; Leino, M.; Lommel, B.; Mann, R.; Papadakis, P.; Rostron, D.; Rudolph, D.; Šáro, Š.; Sulignano, B. (4 February 2011). "Decay study of 246Fm at SHIP" (PDF). The European Physical Journal A. 47 (2): 20. Bibcode:2011EPJA...47...20V. doi:10.1140/epja/i2011-11020-9. ISSN 1434-601X. S2CID 119353521. Retrieved 24 June 2023.

[12] Heßberger, F. P.; Hofmann, S.; Ackermann, D.; Antalic, S.; Kindler, B.; Kojouharov, I.; Kuusiniemi, P.; Leino, M.; Lommel, B.; Mann, R.; Nishio, K.; Popeko, A. G.; Sulignano, B.; Saro, S.; Streicher, B.; Venhart, M.; Yeremin, A. V. (1 December 2006). "Alpha-gamma decay studies of 255Rf, 251No and 247Fm" (PDF). The European Physical Journal A - Hadrons and Nuclei. 30 (3): 561–569. Bibcode:2006EPJA...30..561H. doi:10.1140/epja/i2006-10137-2. ISSN 1434-601X. S2CID 123871572. Retrieved 24 June 2023.

[13] Heßberger, F. P.; Antalic, S.; Ackermann, D.; Kalaninová, Z.; Heinz, S.; Hofmann, S.; Streicher, B.; Kindler, B.; Kojouharov, I.; Kuusiniemi, P.; Leino, M.; Lommel, B.; Mann, R.; Nishio, K.; Šáro, Š.; Sulignano, B.; Venhart, M. (29 May 2012). "Alpha-gamma decay studies of 253No and its daughter products 253Md , 249Fm" (PDF). The European Physical Journal A. 48 (5): 75. Bibcode:2012EPJA...48...75H. doi:10.1140/epja/i2012-12075-8. ISSN 1434-601X. S2CID 254111959. Retrieved 25 June 2023.

[14] Antalic, S.; Heßberger, F. P.; Ackermann, D.; Heinz, S.; Hofmann, S.; Kalaninová, Z.; Kindler, B.; Khuyagbaatar, J.; Kojouharov, I.; Kuusiniemi, P.; Leino, M.; Lommel, B.; Mann, R.; Nishio, K.; Šáro, Š.; Streicher, B.; Sulignano, B.; Venhart, M. (20 May 2011). "Isomeric states in 253No and 253Fm" (PDF). The European Physical Journal A. 47 (5): 62. Bibcode:2011EPJA...47...62A. doi:10.1140/epja/i2011-11062-y. ISSN 1434-601X. S2CID 121080273. Retrieved 25 June 2023.