Isotopes of iron
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Naturally occurring iron (26Fe) consists of four stable isotopes: 5.845% of 54Fe (possibly radioactive with a half-life over 4.4×1020 years),[4] 91.754% of 56Fe, 2.119% of 57Fe and 0.286% of 58Fe. There are 24 known radioactive isotopes, the most stable of which are 60Fe (half-life 2.6 million years) and 55Fe (half-life 2.7 years).
Much of the past work on measuring the isotopic composition of Fe has centered on determining 60Fe variations due to processes accompanying
List of isotopes
Nuclide [n 1] |
Z | N | Isotopic mass (Da) [n 2][n 3] |
Half-life [n 4] |
Daughter isotope [n 6] |
Natural abundance (mole fraction) | |||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Excitation energy | Normal proportion | Range of variation | |||||||||||||||||
45Fe | 26 | 19 | 45.01458(24)# | 1.89(49) ms | β+ (30%) | 45Mn | 3/2+# | ||||||||||||
2p (70%) | 43Cr | ||||||||||||||||||
46Fe | 26 | 20 | 46.00081(38)# | 9(4) ms [12(+4-3) ms] |
β+ (>99.9%) | 46Mn | 0+ | ||||||||||||
β+, p (<.1%) | 45Cr | ||||||||||||||||||
47Fe | 26 | 21 | 46.99289(28)# | 21.8(7) ms | β+ (>99.9%) | 47Mn | 7/2−# | ||||||||||||
β+, p (<.1%) | 46Cr | ||||||||||||||||||
48Fe | 26 | 22 | 47.98050(8)# | 44(7) ms | β+ (96.41%) | 48Mn | 0+ | ||||||||||||
β+, p (3.59%) | 47Cr | ||||||||||||||||||
49Fe | 26 | 23 | 48.97361(16)# | 70(3) ms | β+, p (52%) | 48Cr | (7/2−) | ||||||||||||
β+ (48%) | 49Mn | ||||||||||||||||||
50Fe | 26 | 24 | 49.96299(6) | 155(11) ms | β+ (>99.9%) | 50Mn | 0+ | ||||||||||||
β+, p (<.1%) | 49Cr | ||||||||||||||||||
51Fe | 26 | 25 | 50.956820(16) | 305(5) ms | β+ | 51Mn | 5/2− | ||||||||||||
52Fe | 26 | 26 | 51.948114(7) | 8.275(8) h | β+ | 52mMn | 0+ | ||||||||||||
52mFe | 6.81(13) MeV | 45.9(6) s | β+ | 52Mn | (12+)# | ||||||||||||||
53Fe | 26 | 27 | 52.9453079(19) | 8.51(2) min | β+ | 53Mn | 7/2− | ||||||||||||
53mFe | 3040.4(3) keV | 2.526(24) min | IT
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53Fe | 19/2− | ||||||||||||||
54Fe | 26 | 28 | 53.9396090(5) | Observationally Stable[n 8]
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0+ | 0.05845(35) | 0.05837–0.05861 | ||||||||||||
54mFe | 6526.9(6) keV | 364(7) ns | 10+ | ||||||||||||||||
55Fe | 26 | 29 | 54.9382934(7) | 2.737(11) y | EC | 55Mn | 3/2− | ||||||||||||
56Fe[n 9] | 26 | 30 | 55.9349363(5) | Stable | 0+ | 0.91754(36) | 0.91742–0.91760 | ||||||||||||
57Fe | 26 | 31 | 56.9353928(5) | Stable | 1/2− | 0.02119(10) | 0.02116–0.02121 | ||||||||||||
58Fe | 26 | 32 | 57.9332744(5) | Stable | 0+ | 0.00282(4) | 0.00281–0.00282 | ||||||||||||
59Fe | 26 | 33 | 58.9348755(8) | 44.495(9) d | β− | 59Co | 3/2− | ||||||||||||
60Fe | 26 | 34 | 59.934072(4) | 2.6×106 y | β− | 60Co | 0+ | trace | |||||||||||
61Fe | 26 | 35 | 60.936745(21) | 5.98(6) min | β− | 61Co | 3/2−,5/2− | ||||||||||||
61mFe | 861(3) keV | 250(10) ns | 9/2+# | ||||||||||||||||
62Fe | 26 | 36 | 61.936767(16) | 68(2) s | β− | 62Co | 0+ | ||||||||||||
63Fe | 26 | 37 | 62.94037(18) | 6.1(6) s | β− | 63Co | (5/2)− | ||||||||||||
64Fe | 26 | 38 | 63.9412(3) | 2.0(2) s | β− | 64Co | 0+ | ||||||||||||
65Fe | 26 | 39 | 64.94538(26) | 1.3(3) s | β− | 65Co | 1/2−# | ||||||||||||
65mFe | 364(3) keV | 430(130) ns | (5/2−) | ||||||||||||||||
66Fe | 26 | 40 | 65.94678(32) | 440(40) ms | β− (>99.9%) | 66Co | 0+ | ||||||||||||
β−, n (<.1%) | 65Co | ||||||||||||||||||
67Fe | 26 | 41 | 66.95095(45) | 394(9) ms | β− (>99.9%) | 67Co | 1/2−# | ||||||||||||
β−, n (<.1%) | 66Co | ||||||||||||||||||
67mFe | 367(3) keV | 64(17) µs | (5/2−) | ||||||||||||||||
68Fe | 26 | 42 | 67.95370(75) | 187(6) ms | β− (>99.9%) | 68Co | 0+ | ||||||||||||
β−, n | 67Co | ||||||||||||||||||
69Fe | 26 | 43 | 68.95878(54)# | 109(9) ms | β− (>99.9%) | 69Co | 1/2−# | ||||||||||||
β−, n (<.1%) | 68Co | ||||||||||||||||||
70Fe | 26 | 44 | 69.96146(64)# | 94(17) ms | 0+ | ||||||||||||||
71Fe | 26 | 45 | 70.96672(86)# | 30# ms [>300 ns] |
7/2+# | ||||||||||||||
72Fe | 26 | 46 | 71.96962(86)# | 10# ms [>300 ns] |
0+ | ||||||||||||||
This table header & footer: |
- ^ mFe – 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).
- ^ a b # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
- ^
Modes of decay:
EC: Electron capture IT: Isomeric transitionn: Neutron emission p: Proton emission - ^ Bold symbol as daughter – Daughter product is stable.
- ^ ( ) spin value – Indicates spin with weak assignment arguments.
- a[4]
- ^ Lowest mass per nucleon of all nuclides; End product of stellar nucleosynthesis
- Atomic masses of the stable nuclides (54Fe, 56Fe, 57Fe, and 58Fe) are given by the AME2012 atomic mass evaluation. The one standard deviation errors are given in parentheses after the corresponding last digits.[6]
Iron-54
54Fe is observationally stable, but theoretically can decay to 54Cr, with a half-life of more than 4.4×1020 years via double electron capture (εε).[4]
Iron-56
56Fe is the isotope with the lowest mass per nucleon, 930.412 MeV/c2, though not the isotope with the highest nuclear binding energy per nucleon, which is nickel-62.[7] However, because of the details of how nucleosynthesis works, 56Fe is a more common endpoint of fusion chains inside extremely massive stars and is therefore more common in the universe, relative to other metals, including 62Ni, 58Fe and 60Ni, all of which have a very high binding energy.
Iron-57
57Fe is widely used in Mössbauer spectroscopy and the related nuclear resonance vibrational spectroscopy due to the low natural variation in energy of the 14.4 keV nuclear transition.[8] The transition was famously used to make the first definitive measurement of gravitational redshift, in the 1960 Pound–Rebka experiment.[9]
Iron-58
Iron-58 can be used to combat anemia and low iron absorption, to metabolically track iron-controlling human genes, and for tracing elements in nature.[10][11] Iron-58 is also an assisting reagent in the synthesis of superheavy elements.[11]
Iron-60
Iron-60 is an iron isotope with a half-life of 2.6 million years,[12][13] but was thought until 2009 to have a half-life of 1.5 million years. It undergoes beta decay to cobalt-60, which then decays with a half-life of about 5 years to stable nickel-60. Traces of iron-60 have been found in lunar samples.
In phases of the meteorites Semarkona and Chervony Kut, a correlation between the concentration of 60
Iron-60 found in fossilised bacteria in sea floor sediments suggest there was a supernova in the vicinity of the Solar System approximately 2 million years ago.[14][15] Iron-60 is also found in sediments from 8 million years ago.[16]
In 2019, researchers found interstellar 60Fe in Antarctica, which they relate to the Local Interstellar Cloud.[17]
References
- .
- ^ "Standard Atomic Weights: Iron". CIAAW. 1993.
- ISSN 1365-3075.
- ^ .
- PMID 16463281.
- S2CID 250839471.
- doi:10.1119/1.17828.
- ^ R. Nave. "Mossbauer Effect in Iron-57". HyperPhysics. Georgia State University. Retrieved 2009-10-13.
- .
- ^ "Iron-58 Metal Isotope". American Elements. Retrieved 2023-06-28.
- ^ a b Vasiliev, Petr. "Iron-58, Iron-58 Isotope, Enriched Iron-58, Iron-58 Metal". www.buyisotope.com. Retrieved 2023-06-28.
- PMID 19792637.
- ^ "Eisen mit langem Atem". scienceticker. 27 August 2009. Archived from the original on 3 February 2018. Retrieved 22 May 2010.
- ^ Belinda Smith (Aug 9, 2016). "Ancient bacteria store signs of supernova smattering". Cosmos.
- PMID 27503888.
- .
- S2CID 201868513.
Isotope masses from:
- Audi, Georges; Bersillon, Olivier; Blachot, Jean;
Isotopic compositions and standard atomic masses from:
- .
- Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". .
- "News & Notices: Standard Atomic Weights Revised". International Union of Pure and Applied Chemistry. 19 October 2005.
Half-life, spin, and isomer data selected from:
- Audi, Georges; Bersillon, Olivier; Blachot, Jean;
- 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.). ISBN 978-0-8493-0485-9.
Further reading
- J. M. Nielsen (1960). The Radiochemistry of Iron (PDF). National Research Council.