Isotopes of iron

Isotopes of iron (26Fe)
Main isotopes Decay
abun­dance half-life (t1/2) mode pro­duct
54Fe 5.85% stable
55Fe synth 2.73 y ε 55Mn
56Fe 91.8% stable
57Fe 2.12% stable
58Fe 0.28% stable
59Fe synth 44.6 d β 59Co
60Fe trace 2.6×106 y β 60Co
Standard atomic weight Ar°(Fe)

Naturally occurring iron (26Fe) consists of four stable isotopes: 5.845% of 54Fe (possibly radioactive with a half-life over 4.4×1020 years), 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 nucleosynthesis (i.e., meteorite studies) and ore formation. In the last decade however, advances in mass spectrometry technology have allowed the detection and quantification of minute, naturally occurring variations in the ratios of the stable isotopes of iron. Much of this work has been driven by the Earth and planetary science communities, although applications to biological and industrial systems are beginning to emerge.

List of isotopes

Nuclide
Z N Isotopic mass (Da)
Half-life
Decay
mode

Daughter
isotope

Spin and
parity
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 53Fe 19/2−
54Fe 26 28 53.9396090(5) Observationally Stable 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 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:
  1. ^ mFe – 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. ^ a b # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  5. ^ Modes of decay:
    EC: Electron capture
    IT: Isomeric transition
    n: Neutron emission
    p: Proton emission
  6. ^ Bold symbol as daughter – Daughter product is stable.
  7. ^ ( ) spin value – Indicates spin with weak assignment arguments.
  8. ^ Believed to decay by β+β+ to 54Cr with a half-life of over 4.4×1020 a
  9. ^ 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.

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).

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. 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. The transition was famously used to make the first definitive measurement of gravitational redshift, in the 1960 Pound–Rebka experiment.

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. Iron-58 is also an assisting reagent in the synthesis of superheavy elements.

Iron-60

Iron-60 is an iron isotope with a half-life of 2.6 million years, 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 60Ni, the granddaughter isotope of 60Fe, and the abundance of the stable iron isotopes could be found, which is evidence for the existence of 60Fe at the time of formation of the Solar System. Possibly the energy released by the decay of 60Fe contributed, together with the energy released by decay of the radionuclide 26Al, to the remelting and differentiation of asteroids after their formation 4.6 billion years ago. The abundance of 60Ni present in extraterrestrial material may also provide further insight into the origin of the Solar System and its early history.

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. Iron-60 is also found in sediments from 8 million years ago.

In 2019, researchers found interstellar 60Fe in Antarctica, which they relate to the Local Interstellar Cloud.


This page was last updated at 2024-04-17 14:35 UTC. Update now. View original page.

All our content comes from Wikipedia and under the Creative Commons Attribution-ShareAlike License.


Top

If mathematical, chemical, physical and other formulas are not displayed correctly on this page, please useFirefox or Safari