Isotopes of iron

{{Short description|none}} {{Infobox iron isotopes}} Natural iron ({{sub|26}}Fe) consists of four stable isotopes: 5.85% {{sup|54}}Fe, 91.75% {{sup|56}}Fe, 2.12% {{sup|57}}Fe and 0.28% {{sup|58}}Fe. There are 28 known radioisotopes and 8 nuclear isomers, the most stable of which are {{sup|60}}Fe (half-life 2.62 million years) and {{sup|55}}Fe (half-life 2.7562 years).

Much of the past work on measuring the isotopic composition of iron has centered on determining {{sup|60}}Fe variations due to processes accompanying nucleosynthesis (e.g., 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, though applications to biological and industrial systems are beginning to emerge.<ref>{{cite journal |author=N. Dauphas |author2=O. Rouxel |year=2006 |title=Mass spectrometry and natural variations of iron isotopes |journal=Mass Spectrometry Reviews |volume=25 |issue= 4|pages=515–550 |doi=10.1002/mas.20078 |pmid=16463281|bibcode=2006MSRv...25..515D }}</ref>

== List of isotopes == {{anchor|Iron-47m}} <!--Please delete anchor(s) from the heading above or table below if adding a dedicated isotope section(s).--> {{Isotopes table |symbol=Fe |refs=NUBASE2020, AME2020 II, IsotopeFRIB, IsomerFRIB |notes=m, unc(), mass#, hl#, spin(), spin#, daughter-st, EC, IT, n, p, discoveryname }} |-id=Iron-45 | rowspan=4|⁴⁵Fe | rowspan=4 style="text-align:right" | 26 | rowspan=4 style="text-align:right" | 19 | rowspan=4|45.01547(30)# | rowspan=4 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/45.pdf 1996] | rowspan=4|2.5(2)&nbsp;ms | 2p (70%) | ⁴³Cr | rowspan=4|3/2+# | rowspan=4| | rowspan=4| |- | β⁺, p (18.9%) | ⁴⁴Cr |- | β⁺, 2p (7.8%) | ⁴³V |- | β⁺ (3.3%) | ⁴⁵Mn |-id=Iron-46 | rowspan=3|⁴⁶Fe | rowspan=3 style="text-align:right" | 26 | rowspan=3 style="text-align:right" | 20 | rowspan=3|46.00130(32)# | rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/46.pdf 1992] | rowspan=3|13.0(20)&nbsp;ms | β⁺, p (78.7%) | ⁴⁵Cr | rowspan=3|0+ | rowspan=3| | rowspan=3| |- | β⁺ (21.3%) | ⁴⁶Mn |- | β⁺, 2p? | ⁴⁴V |-id=Iron-47 | rowspan=2|⁴⁷Fe | rowspan=2 style="text-align:right" | 26 | rowspan=2 style="text-align:right" | 21 | rowspan=2|46.99235(54)# | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/47.pdf 1992] | rowspan=2|21.9(2)&nbsp;ms | β⁺, p (88.4%) | ⁴⁶Cr | rowspan=2|7/2−# | rowspan=2| | rowspan=2| |- | β⁺ (11.6%) | ⁴⁷Mn |-id=Iron-48 | rowspan=2|⁴⁸Fe | rowspan=2 style="text-align:right" | 26 | rowspan=2 style="text-align:right" | 22 | rowspan=2|47.980667(99) | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/48.pdf 1987] | rowspan=2|45.3(6)&nbsp;ms | β⁺ (84.7%) | ⁴⁸Mn | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β⁺, p (15.3%) | ⁴⁷Cr |-id=Iron-49 | rowspan=2|⁴⁹Fe | rowspan=2 style="text-align:right" | 26 | rowspan=2 style="text-align:right" | 23 | rowspan=2|48.973429(26) | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/49.pdf 1970] | rowspan=2|64.7(3)&nbsp;ms | β⁺, p (56.7%) | ⁴⁸Cr | rowspan=2|(7/2−) | rowspan=2| | rowspan=2| |- | β⁺ (43.3%) | ⁴⁹Mn |-id=Iron-50 | rowspan=2|⁵⁰Fe | rowspan=2 style="text-align:right" | 26 | rowspan=2 style="text-align:right" | 24 | rowspan=2|49.9629880(90) | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/50.pdf 1977] | rowspan=2|152.0(6)&nbsp;ms | β⁺ | ⁵⁰Mn | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β⁺, p? | ⁴⁹Cr |-id=Iron-51 | ⁵¹Fe | style="text-align:right" | 26 | style="text-align:right" | 25 | 50.9568551(15) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/51.pdf 1972] | 305.4(23)&nbsp;ms | β⁺ | ⁵¹Mn | 5/2− | | |-id=Iron-52 | ⁵²Fe | style="text-align:right" | 26 | style="text-align:right" | 26 | 51.94811336(19) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/52.pdf 1948] | 8.275(8)&nbsp;h | β⁺ | ⁵²Mn | 0+ | | |-id=Iron-52m | rowspan=2 style="text-indent:1em" | ^52mFe | rowspan=2 colspan="3" style="text-indent:2em" | 6960.7(3)&nbsp;keV | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/26/52Fe-1.pdf 1975] | rowspan=2|45.9(6)&nbsp;s | β⁺ (99.98%) | ⁵²Mn | rowspan=2|12+ | rowspan=2| | rowspan=2| |- | IT (0.021%) | ⁵²Fe |-id=Iron-53 | ⁵³Fe | style="text-align:right" | 26 | style="text-align:right" | 27 | 52.9453056(18) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/53.pdf 1938] | 8.51(2)&nbsp;min | β⁺ | ⁵³Mn | 7/2− | | |-id=Iron-53m | style="text-indent:1em" | ^53mFe | colspan="3" style="text-indent:2em" | 3040.4(3)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/26/53Fe-1.pdf 1966] | 2.54(2)&nbsp;min | IT | ⁵³Fe | 19/2− | | |-id=Iron-54 | ⁵⁴Fe | style="text-align:right" | 26 | style="text-align:right" | 28 | 53.93960819(37) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/54.pdf 1924] | colspan=3 align=center|'''Observationally Stable'''{{refn|group=n|Believed to decay by β⁺β⁺ to '''⁵⁴Cr''' with a half-life of over 4.4×10²⁰ a<ref name="Fe54decay">{{cite journal |last1=Bikit |first1=I. |last2=Krmar |first2=M. |last3=Slivka |first3=J. |last4=Vesković |first4=M. |last5=Čonkić |first5=Lj. |last6=Aničin |first6=I. |title=New results on the double β decay of iron |journal=Physical Review C |date=1998 |volume=58 |issue=4 |pages=2566–2567 |doi=10.1103/PhysRevC.58.2566|bibcode=1998PhRvC..58.2566B }}</ref>}} | 0+ | 0.05845(105) | |-id=Iron-54m | style="text-indent:1em" | ^54mFe | colspan="3" style="text-indent:2em" | 6527.1(11)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/26/54Fe-1.pdf 1978] | 364(7)&nbsp;ns | IT | '''⁵⁴Fe''' | 10+ | | |-id=Iron-55 | ⁵⁵Fe | style="text-align:right" | 26 | style="text-align:right" | 29 | 54.93829116(33) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/55.pdf 1939] | 2.7562(4)&nbsp;y | EC | '''⁵⁵Mn''' | 3/2− | | |-id=Iron-56 | ⁵⁶Fe<ref group="n">Lowest mass per nucleon of all nuclides; End product of stellar nucleosynthesis</ref> | style="text-align:right" | 26 | style="text-align:right" | 30 | 55.93493554(29) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/56.pdf 1922] | colspan=3 align=center|'''Stable''' | 0+ | 0.91754(106) | |-id=Iron-57 | ⁵⁷Fe | style="text-align:right" | 26 | style="text-align:right" | 31 | 56.93539195(29) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/57.pdf 1935] | colspan=3 align=center|'''Stable''' | 1/2− | 0.02119(29) | |-id=Iron-58 | ⁵⁸Fe | style="text-align:right" | 26 | style="text-align:right" | 32 | 57.93327358(34) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/58.pdf 1935] | colspan=3 align=center|'''Stable''' | 0+ | 0.00282(12) | |-id=Iron-59 | ⁵⁹Fe | style="text-align:right" | 26 | style="text-align:right" | 33 | 58.93487349(35) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/59.pdf 1938] | 44.500(12)&nbsp;d | β⁻ | '''⁵⁹Co''' | 3/2− | | |-id=Iron-60 | ⁶⁰Fe | style="text-align:right" | 26 | style="text-align:right" | 34 | 59.9340702(37) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/60.pdf 1957] | 2.62(4)×10⁶&nbsp;y | β⁻ | ⁶⁰Co | 0+ | trace | |-id=Iron-61 | ⁶¹Fe | style="text-align:right" | 26 | style="text-align:right" | 35 | 60.9367462(28) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/61.pdf 1957] | 5.98(6)&nbsp;min | β⁻ | ⁶¹Co | (3/2−) | | |-id=Iron-61m | style="text-indent:1em" | ^61mFe | colspan="3" style="text-indent:2em" | 861.67(11)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/26/61Fe-1.pdf 1998] | 238(5)&nbsp;ns | IT | ⁶¹Fe | 9/2+ | | |-id=Iron-62 | ⁶²Fe | style="text-align:right" | 26 | style="text-align:right" | 36 | 61.9367918(30) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/62.pdf 1975] | 68(2)&nbsp;s | β⁻ | ⁶²Co | 0+ | | |-id=Iron-63 | ⁶³Fe | style="text-align:right" | 26 | style="text-align:right" | 37 | 62.9402727(46) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/63.pdf 1980] | 6.1(6)&nbsp;s | β⁻ | ⁶³Co | (5/2−) | | |-id=Iron-64 | ⁶⁴Fe | style="text-align:right" | 26 | style="text-align:right" | 38 | 63.9409878(54) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/64.pdf 1980] | 2.0(2)&nbsp;s | β⁻ | ⁶⁴Co | 0+ | | |-id=Iron-65 | rowspan=2|⁶⁵Fe | rowspan=2 style="text-align:right" | 26 | rowspan=2 style="text-align:right" | 39 | rowspan=2|64.9450153(55) | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/65.pdf 1985] | rowspan=2|805(10)&nbsp;ms | β⁻ | ⁶⁵Co | rowspan=2|(1/2−) | rowspan=2| | rowspan=2| |- | β⁻, n? | ⁶⁴Co |-id=Iron-65m1 | style="text-indent:1em" | ^65m1Fe | colspan="3" style="text-indent:2em" | 393.7(2)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/26/65Fe-2.pdf 1999] | 1.12(15)&nbsp;s | β⁻? | ⁶⁵Co | (9/2+) | | |-id=Iron-65m2 | style="text-indent:1em" | ^65m2Fe | colspan="3" style="text-indent:2em" | 397.6(2)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/26/65Fe-1.pdf 1998] | 418(12)&nbsp;ns | IT | ⁶⁵Fe | (5/2+) | | |-id=Iron-66 | rowspan=2|⁶⁶Fe | rowspan=2 style="text-align:right" | 26 | rowspan=2 style="text-align:right" | 40 | rowspan=2|65.9462500(44) | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/66.pdf 1985] | rowspan=2|467(29)&nbsp;ms | β⁻ | ⁶⁶Co | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β⁻, n? | ⁶⁵Co |-id=Iron-67 | rowspan=2|⁶⁷Fe | rowspan=2 style="text-align:right" | 26 | rowspan=2 style="text-align:right" | 41 | rowspan=2|66.9509300(41) | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/67.pdf 1985] | rowspan=2|394(9)&nbsp;ms | β⁻ | ⁶⁷Co | rowspan=2|(1/2-) | rowspan=2| | rowspan=2| |- | β⁻, n? | ⁶⁶Co |-id=Iron-67m1 | style="text-indent:1em" | ^67m1Fe | colspan="3" style="text-indent:2em" | 403(9)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/26/67Fe-1.pdf 1998] | 64(17)&nbsp;μs | IT | ⁶⁷Fe | (5/2+,7/2+) | | |-id=Iron-67m2 | style="text-indent:1em" | ^67m2Fe | colspan="3" style="text-indent:2em" | 450(100)#&nbsp;keV | (2003){{refn|group=n|Not clear this is a different isomer; it has only been suggested<ref>{{cite journal |last1=Sawicka |first1=M. |last2=Daugas |first2=J.M. |last3=Grawe|first3=H. |last4=Cwiok |first4=S. |last5=Balabanski |first5=D.L. |display-authors=etal |title=Isomeric decay of ⁶⁷Fe -- Evidence for deformation |journal=Eur. Phys. J. A |date=2003|volume=16 |pages=51 |doi=10.1140/epja/i2002-10073-1 }}</ref>}} | 75(21)&nbsp;μs | IT | ⁶⁷Fe | (9/2+) | | |-id=Iron-68 | rowspan=2|⁶⁸Fe | rowspan=2 style="text-align:right" | 26 | rowspan=2 style="text-align:right" | 42 | rowspan=2|67.95288(21)# | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/68.pdf 1985] | rowspan=2|188(4)&nbsp;ms | β⁻ | ⁶⁸Co | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β⁻, n? | ⁶⁷Co |-id=Iron-69 | rowspan=3|⁶⁹Fe | rowspan=3 style="text-align:right" | 26 | rowspan=3 style="text-align:right" | 43 | rowspan=3|68.95792(22)# | rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/69.pdf 1992] | rowspan=3|162(7)&nbsp;ms | β⁻ | ⁶⁹Co | rowspan=3|1/2−# | rowspan=3| | rowspan=3| |- | β⁻, n? | ⁶⁸Co |- | β⁻, 2n? | ⁶⁷Co |-id=Iron-70 | rowspan=2|⁷⁰Fe | rowspan=2 style="text-align:right" | 26 | rowspan=2 style="text-align:right" | 44 | rowspan=2|69.96040(32)# | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/70.pdf 1997] | rowspan=2|61.4(7)&nbsp;ms | β⁻ | ⁷⁰Co | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β⁻, n? | ⁶⁹Co

|-id=Iron-71 | rowspan=3|⁷¹Fe | rowspan=3 style="text-align:right" | 26 | rowspan=3 style="text-align:right" | 45 | rowspan=3|70.96572(43)# | rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/71.pdf 1997] | rowspan=3|34.3(26)&nbsp;ms | β⁻ | ⁷¹Co | rowspan=3|7/2+# | rowspan=3| | rowspan=3| |- | β⁻, n? | ⁷⁰Co |- | β⁻, 2n? | ⁶⁹Co |-id=Iron-72 | rowspan=3|⁷²Fe | rowspan=3 style="text-align:right" | 26 | rowspan=3 style="text-align:right" | 46 | rowspan=3|71.96860(54)# | rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/72.pdf 1997] | rowspan=3|17.0(10)&nbsp;ms | β⁻ | ⁷²Co | rowspan=3|0+ | rowspan=3| | rowspan=3| |- | β⁻, n? | ⁷¹Co |- | β⁻, 2n? | ⁷⁰Co |-id=Iron-73 | rowspan=3|⁷³Fe | rowspan=3 style="text-align:right" | 26 | rowspan=3 style="text-align:right" | 47 | rowspan=3|72.97425(54)# | rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/73.pdf 2010] | rowspan=3|12.9(16)&nbsp;ms | β⁻ | ⁷³Co | rowspan=3|7/2+# | rowspan=3| | rowspan=3| |- | β⁻, n? | ⁷²Co |- | β⁻, 2n? | ⁷¹Co |-id=Iron-74 | rowspan=3|⁷⁴Fe | rowspan=3 style="text-align:right" | 26 | rowspan=3 style="text-align:right" | 48 | rowspan=3|73.97782(54)# | rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/74.pdf 2010] | rowspan=3|5(5)&nbsp;ms | β⁻ | ⁷⁴Co | rowspan=3|0+ | rowspan=3| | rowspan=3| |- | β⁻, n? | ⁷³Co |- | β⁻, 2n? | ⁷²Co |-id=Iron-75 | rowspan=3|⁷⁵Fe | rowspan=3 style="text-align:right" | 26 | rowspan=3 style="text-align:right" | 49 | rowspan=3|74.98422(64)# | rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/75.pdf 2013] | rowspan=3|9#&nbsp;ms<br />[>620&nbsp;ns] | β⁻? | ⁷⁵Co | rowspan=3|9/2+# | rowspan=3| | rowspan=3| |- | β⁻, n? | ⁷⁴Co |- | β⁻, 2n? | ⁷³Co |-id=Iron-76 | ⁷⁶Fe | style="text-align:right" | 26 | style="text-align:right" | 50 | 75.98863(64)# | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/76.pdf 2017] | 3#&nbsp;ms<br />[>410&nbsp;ns] | β⁻? | ⁷⁶Co | 0+ | | |-id=Iron-77 | ⁷⁷Fe<ref name="Shimizu2026">{{cite journal |last1=Shimizu |first1=Y |last2=Rykaczewski |first2=K P |last3=Fukuda |first3=N |last4=Brewer |first4=N T |last5=Dillmann |first5=I |last6=Grzywacz |first6=R K |last7=Nishimura |first7=S |last8=Rasco |first8=B C |last9=Tain |first9=J L |last10=Suzuki |first10=H |last11=Takeda |first11=H |last12=Ahn |first12=D S |last13=Sumikama |first13=T |last14=Inabe |first14=N |last15=Yoshida |first15=K |last16=Ueno |first16=H |last17=Michimasa |first17=S |last18=Algora |first18=A |last19=Allmond |first19=J M |last20=Agramunt |first20=J |last21=Baba |first21=H |last22=Bae |first22=S |last23=Bruno |first23=C G |last24=Caballero-Folch |first24=R |last25=Calvino |first25=F |last26=Coleman-Smith |first26=P J |last27=Cortes |first27=G |last28=Davinson |first28=T |last29=Domingo-Pardo |first29=C |last30=Estrade |first30=A |last31=Go |first31=S |last32=Griffin |first32=C J |last33=Ha |first33=J |last34=Hall |first34=O |last35=Harkness-Brennan |first35=L J |last36=Heideman |first36=J |last37=Isobe |first37=T |last38=Kahl |first38=D |last39=Karny |first39=M |last40=Khiem |first40=L H |last41=King |first41=T T |last42=Kiss |first42=G G |last43=Korgul |first43=A |last44=Kubono |first44=S |last45=Labiche |first45=M |last46=Lazarus |first46=I |last47=Liang |first47=J |last48=Liu |first48=J |last49=Lorusso |first49=G |last50=Madurga |first50=M |last51=Matsui |first51=K |last52=Miernik |first52=K |last53=Montes |first53=F |last54=Morales |first54=A I |last55=Morrall |first55=P |last56=Nepal |first56=N |last57=Page |first57=R D |last58=Phong |first58=V H |last59=Piersa-Siłkowska |first59=M |last60=Prydderch |first60=M |last61=Pucknell |first61=V F E |last62=Rajabali |first62=M M |last63=Rubio |first63=B |last64=Saito |first64=Y |last65=Sakurai |first65=H |last66=Simpson |first66=J |last67=Singh |first67=M |last68=Stracener |first68=D W |last69=Tarifeño-Saldivia |first69=A |last70=Thomas |first70=S L |last71=Tolosa-Delgado |first71=A |last72=Wolinska-Cichocka |first72=M |last73=Woods |first73=P J |last74=Xu |first74=X X |last75=Yokoyama |first75=R |title=Exploration of Neutron-Rich Isotopes around N = 50 via the In-Flight Fission of a 345 MeV/Nucleon 238U Beam |journal=Progress of Theoretical and Experimental Physics |date=6 March 2026 |volume=2026 |issue=3 |doi=10.1093/ptep/ptag036|hdl=2117/462425 |hdl-access=free }}</ref> | style="text-align:right" | 26 | style="text-align:right" | 51 | | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/26/77.pdf 2026] | | | | | {{Isotopes table/footer}}

==Iron-56== {{main|Iron-56}} {{sup|56}}Fe is the most abundant isotope of iron. It is also the isotope with the lowest mass per nucleon, 930.412 MeV/c{{sup|2}}, though not the isotope with the highest nuclear binding energy per nucleon, which is nickel-62.<ref>{{cite journal |url=https://ui.adsabs.harvard.edu/abs/1995AmJPh..63..653F/abstract |journal=American Journal of Physics|bibcode=1995AmJPh..63..653F|title=The atomic nuclide with the highest mean binding energy|last1=Fewell|first1=M. P.|year=1995|volume=63|issue=7|page=653|doi=10.1119/1.17828}}</ref> However, because of the details of how nucleosynthesis works, {{sup|56}}Fe is a more common endpoint of fusion inside supernovae, where it is mostly produced as {{sup|56}}Ni, which subsequently decays to {{sup|56}}Co and then iron. Thus, {{sup|56}}Fe is more common in the universe, relative to other heavy elements, including {{sup|62}}Ni, {{sup|58}}Fe, and {{sup|60}}Ni, all of which have a comparably high binding energy.

== Iron-57 == {{sup|57}}Fe 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&nbsp;keV nuclear transition.<ref> {{cite web |author=R. Nave |title=Mossbauer Effect in Iron-57 |url=http://hyperphysics.phy-astr.gsu.edu/Hbase/Nuclear/mossfe.html |work=HyperPhysics |publisher=Georgia State University |access-date=2009-10-13 }}</ref> The transition was famously used to make the first definitive measurement of gravitational redshift, in the 1960 Pound–Rebka experiment.<ref>{{cite journal|last=Pound| first=R. V.|author2=Rebka Jr. G. A. | date= April 1, 1960| title=Apparent weight of photons| journal=Physical Review Letters| volume=4| issue=7| pages=337–341| doi = 10.1103/PhysRevLett.4.337| bibcode=1960PhRvL...4..337P| doi-access=free}}</ref>

== Iron-60 == '''Iron-60''' has a half-life of 2.62&nbsp;million years,<ref>{{cite journal|title=New Measurement of the {{sup|60}}Fe Half-Life |journal=Physical Review Letters |volume=103 |issue= 7|article-number=72502 |doi=10.1103/PhysRevLett.103.072502|pmid=19792637 |bibcode=2009PhRvL.103g2502R|year=2009|last1=Rugel|first1=G.|last2=Faestermann|first2=T.|last3=Knie|first3=K.|last4=Korschinek|first4=G.|last5=Poutivtsev|first5=M.|last6=Schumann|first6=D.|last7=Kivel|first7=N.|last8=Günther-Leopold|first8=I.|last9=Weinreich|first9=R.|last10=Wohlmuther|first10=M.|url=https://www.dora.lib4ri.ch/psi/islandora/object/psi%3A17743 }}</ref> but was thought until 2009 to have a half-life of 1.5&nbsp;million years. It undergoes beta decay to ⁶⁰Co, which then decays with the much shorter half-life of about 5 years to stable ⁶⁰Ni.

In phases of the meteorites ''Semarkona'' and ''Chervony Kut'', a correlation between the excess concentration of {{sup|60}}Ni, the granddaughter isotope of {{sup|60}}Fe, and the abundance of the stable iron isotopes could be found, which is evidence for the existence of {{sup|60}}Fe at the time of formation of the Solar System.<ref>{{cite journal |title=Evidence for live 60Fe in meteorites |date=2004 |last1=Mostefaoui |first1=S. |last2=Lugmair |first2=G.W. |last3=Hoppe |first3=P. |last4=El Goresy |first4=A. |journal=New Astronomy Reviews |volume=48 |issue=1–4 |pages=155–59 |doi=10.1016/j.newar.2003.11.022 |bibcode=2004NewAR..48..155M}}</ref> Depending on its original abundance, the energy from the decay of {{sup|60}}Fe may have been significant, along with that of {{sup|26}}Al, to the remelting and differentiation of asteroids and planetesimals after their formation. These nickel abundances in extraterrestrial materials may also provide further insight into the origin of the Solar System and its early history.

Live (interstellar) iron-60 was first identified in deep sea sediments in 1999.<ref>{{Cite journal |last1=Knie |first1=K. |last2=Korschinek |first2=G. |last3=Faestermann |first3=T. |last4=Wallner |first4=C. |last5=Scholten |first5=J. |last6=Hillebrandt |first6=W. |date=1999-07-01 |title=Indication for Supernova Produced 60Fe Activity on Earth |url=https://ui.adsabs.harvard.edu/abs/1999PhRvL..83...18K |journal=Physical Review Letters |volume=83 |issue=1 |pages=18–21 |bibcode=1999PhRvL..83...18K |doi=10.1103/PhysRevLett.83.18 |issn=0031-9007}}</ref> These are deep sea ferromanganese crusts, which are constantly growing, aggregating iron, manganese, and other elements.<ref name=":3">{{Cite journal |last1=Wallner |first1=A. |last2=Froehlich |first2=M. B. |last3=Hotchkis |first3=M. A. C. |last4=Kinoshita |first4=N. |last5=Paul |first5=M. |last6=Martschini |first6=M. |last7=Pavetich |first7=S. |last8=Tims |first8=S. G. |last9=Kivel |first9=N. |last10=Schumann |first10=D. |last11=Honda |first11=M. |last12=Matsuzaki |first12=H. |last13=Yamagata |first13=T. |date=2021-05-01 |title=60Fe and 244Pu deposited on Earth constrain the r-process yields of recent nearby supernovae |url=https://ui.adsabs.harvard.edu/abs/2021Sci...372..742W |journal=Science |volume=372 |issue=6543 |pages=742–745 |bibcode=2021Sci...372..742W |doi=10.1126/science.aax3972 |issn=0036-8075 |pmid=33986180}}</ref> Iron-60 has been found in fossilized bacteria in sea floor sediments.<ref>{{cite journal|first1=Belinda|last1=Smith|title=Ancient bacteria store signs of supernova smattering|journal=Cosmos|date=August 9, 2016|url=https://cosmosmagazine.com/space/ancient-bacteria-store-signs-of-supernova-smattering}}</ref><ref>{{cite journal|first1=Peter|last1=Ludwig|display-authors=etal|title=Time-resolved 2-million-year-old supernova activity discovered in Earth's microfossil record|journal=PNAS|volume=113|issue=33|pages=9232–9237|date=August 16, 2016|doi=10.1073/pnas.1601040113|pmid=27503888|pmc=4995991|arxiv=1710.09573|bibcode=2016PNAS..113.9232L|doi-access=free}}</ref> In 2019, researchers found {{sup|60}}Fe in Antarctica.<ref name="Interstellar Iron">{{cite journal |title=Interstellar {{sup|60}}Fe in Antarctica |first1=Dominik |last1=Koll |display-authors=etal |journal=Physical Review Letters |year=2019 |volume=123 |issue=7 |article-number=072701 |doi=10.1103/PhysRevLett.123.072701|pmid=31491090 |bibcode=2019PhRvL.123g2701K |s2cid=201868513 |hdl=1885/298253 |hdl-access=free }}</ref> Iron-60 shows two peaks in deep sea sediments, the first 1.7–3.2 million years ago and the second 6.5–8.7 million years ago. The peaks are related to the passage of the Solar System through the Local Bubble and likely the Orion–Eridanus Superbubble. These superbubbles were created by multiple supernovae.<ref name=":2">{{Cite journal |last1=Schulreich |first1=M. M. |last2=Feige |first2=J. |last3=Breitschwerdt |first3=D. |date=2023-12-01 |title=Numerical studies on the link between radioisotopic signatures on Earth and the formation of the Local Bubble. II. Advanced modelling of interstellar 26Al, 53Mn, 60Fe, and 244Pu influxes as traces of past supernova activity in the solar neighbourhood |url=https://ui.adsabs.harvard.edu/abs/2023A&A...680A..39S |journal=Astronomy and Astrophysics |volume=680 |pages=A39 |arxiv=2309.13983 |bibcode=2023A&A...680A..39S |doi=10.1051/0004-6361/202347532 |issn=0004-6361}}</ref> Traces of iron-60 have also been found in lunar samples.

The distance to the supernova of origin can be estimated by relating the amount of iron-60 intercepted as Earth passes through the expanding supernova ejecta. Assuming that the material ejected in a supernova expands uniformly out from its origin as a sphere with surface area 4''πr''{{sup|2}}. The fraction of the material intercepted by the Earth is dependent on its cross-sectional area ({{subsup|''πR''|Earth|2}}) as it passes through the expanding debris:

<math display="block">M_{\text {Fraction intercepted }}=\frac{\pi R_{\text {Earth }}^{2}}{4 \pi r^{2}} M_{e j}</math>

where ''M''{{sub|ej}} is the mass of ejected material. Assuming the intercepted material is distributed uniformly across the surface of the Earth ({{subsup|4''πR''|Earth|2}}), the mass surface density (''Σ''{{sub|ej}}) of the supernova ejecta on Earth is:

<math display="block"> \Sigma_{e j}=\frac{M_{\text {Fraction intercepted }}}{A_{\text {surface,Earth }}}=\frac{M_{e j}}{16 \pi r^2}</math>

The number of {{sup|60}}Fe atoms per unit area found on Earth can be estimated if the typical amount of {{sup|60}}Fe ejected from a supernova is known. This can be done by dividing the surface mass density (''Σ''{{sub|ej}}) by the atomic mass of {{sup|60}}Fe.

<math display="block"> N_{60}=\left(\frac{M_{e j, 60} / m_{60}}{16 \pi r^2}\right) </math>

The equation for ''N''{{sup|60}} can be rearranged to find the distance to the supernova.

<math display="block"> r=\sqrt{\frac{M_{e j, 60}}{16 \pi m_{60} N_{60}}} </math>

An example calculation for the distance to the supernova point of origin is given below. This calculation uses speculative values for terrestrial {{sup|60}}Fe atom surface density (''N''{{sub|60}} ≈ 4 × 10{{sup|11}} atoms/m{{sup|2}}) and a rough estimate of the mass of {{sup|60}}Fe ejected by a supernova ({{val|10|e=-5|u=solar mass}}).

<math display="block">\begin{align} r&=\sqrt{\frac{10^{-5} M_{\odot}}{16 \pi\left(60 m_p\right) N_{60}}} \\ r&=3 \times 10^{18} m=100 p c \end{align}</math>

More sophisticated analyses have been reported that take into consideration the flux and deposition of {{sup|60}}Fe as well as possible interfering background sources.<ref>{{Cite journal |last1=Ertel |first1=Adrienne F. |last2=Fry |first2=Brian J. |last3=Fields |first3=Brian D. |last4=Ellis |first4=John |date=20 April 2023 |title=Supernova Dust Evolution Probed by Deep-sea 60Fe Time History |journal=The Astrophysical Journal |volume=947 |issue=2 |pages=58–83 |doi=10.3847/1538-4357/acb699 |doi-access=free }}</ref>

Cobalt-60, the decay product of iron-60, emits 1.173&nbsp;MeV and 1.332&nbsp;MeV gamma rays as it decays. These lines have long been important targets for gamma-ray astronomy, and have been detected by the gamma-ray observatory INTEGRAL. The signal traces the Galactic plane, showing that {{sup|60}}Fe synthesis is ongoing in our galaxy, and probing element production in massive stars.<ref>{{Cite journal |last1=Harris |first1=M. J. |last2=Knödlseder |first2=J. |last3=Jean |first3=P. |last4=Cisana |first4=E. |last5=Diehl |first5=R. |last6=Lichti |first6=G. G. |last7=Roques |first7=J.-P. |last8=Schanne |first8=S. |last9=Weidenspointner |first9=G. |date=2005-04-01 |title=Detection of γ-ray lines from interstellar 60Fe by the high resolution spectrometer SPI |url=https://ui.adsabs.harvard.edu/abs/2005A&A...433L..49H |journal=Astronomy and Astrophysics |volume=433 |issue=3 |pages=L49–L52 |doi=10.1051/0004-6361:200500093 |arxiv=astro-ph/0502219 |bibcode=2005A&A...433L..49H |issn=0004-6361}}</ref><ref>{{Cite journal |last1=Wang |first1=W. |last2=Siegert |first2=T. |last3=Dai |first3=Z. G. |last4=Diehl |first4=R. |last5=Greiner |first5=J. |last6=Heger |first6=A. |last7=Krause |first7=M. |last8=Lang |first8=M. |last9=Pleintinger |first9=M. M. M. |last10=Zhang |first10=X. L. |date=2020-02-01 |title=Gamma-Ray Emission of 60Fe and 26Al Radioactivity in Our Galaxy |journal=The Astrophysical Journal |volume=889 |issue=2 |page=169 |doi=10.3847/1538-4357/ab6336 |doi-access=free |arxiv=1912.07874 |bibcode=2020ApJ...889..169W |issn=0004-637X}}</ref>

== See also == '''Daughter products other than iron''' * Isotopes of cobalt * Isotopes of manganese * Isotopes of chromium * Isotopes of vanadium

== References == {{Reflist}}

==Further reading== *{{cite book |author=J. M. Nielsen |year=1960 |title=The Radiochemistry of Iron |url=http://library.lanl.gov/cgi-bin/getfile?rc000015.pdf |publisher=National Academy of Sciences/National Research Council }}

{{Navbox element isotopes}}

Category:Isotopes of iron Category:Iron Iron