Iron-55

Iron-55 decays via electron capture to manganese-55 with a half-life of 2.737 years.{{cite journal| first = Audi| last = Georges|title = The NUBASE Evaluation of Nuclear and Decay Properties| journal = Nuclear Physics A| volume = 729| issue = 1| pages = 3–128| year = 2003| doi=10.1016/j.nuclphysa.2003.11.001| bibcode=2003NuPhA.729....3A| citeseerx = 10.1.1.692.8504}} The electrons around the nucleus rapidly adjust themselves to the lowered charge without leaving their shell, and shortly thereafter the vacancy in the "K" shell left by the nuclear-captured electron is filled by an electron from a higher shell. The difference in energy is released by emitting Auger electrons of 5.19 keV, with a probability of about 60%, K-alpha-1 X-rays with energy of 5.89875 keV and a probability about 16.2%, K-alpha-2 X-rays with energy of 5.88765 keV and a probability of about 8.2%, or K-beta X-rays with nominal energy of 6.49045 keV and a probability about 2.85%. The energies of the K-alpha-1 and -2 X-rays are so similar that they are often specified as mono-energetic radiation with 5.9 keV photon energy. Its probability is about 28%.{{cite book|url = https://books.google.com/books?id=Ko_6HhE8fHIC&pg=PA26|isbn = 978-1-4020-1294-5|title = Handbook on radiation probing, gauging, imaging and analysis| author = Esam M. A. Hussein| publisher = Springer| year = 2003| page = 26}} The remaining 12% is accounted for by lower-energy Auger electrons and a few photons from other, minor transitions.

The K-alpha X-rays emitted by the manganese-55 after the electron capture have been used as a laboratory source of X-rays in various X-ray scattering techniques. The advantages of the emitted X-rays are that they are monochromatic and are continuously produced over a years-long period.{{cite journal|doi =10.1063/1.1754691|title =Demonstration of X-ray Diffraction by LiF using the Mn Kα X-rays Resulting From ⁵⁵Fe decay|year =1966|last1 =Preuss|first1 =Luther E.|journal =Applied Physics Letters|volume =9|pages =159–161|bibcode = 1966ApPhL...9..159P|issue =4 }} No electrical power is needed for this emission, which is ideal for portable X-ray instruments, such as X-ray fluorescence instruments.{{cite book|title = Toxic Materials in the Atmosphere, Sampling and Analysis| author = Himmelsbach, B.| isbn = 978-0-8031-0603-1|chapter = Portable X-ray Survey Meters for In Situ Trace element Monitoring of Air Particulates| year = 1982}} The ExoMars mission of ESA used, in 2016,{{cite web| url = http://exploration.esa.int/science-e/www/object/index.cfm?fobjectid=45084| title = The ESA-NASA ExoMars Programme Rover, 2018| publisher = ESA| accessdate = 2010-03-12| archive-url = https://web.archive.org/web/20091223032943/http://exploration.esa.int/science-e/www/object/index.cfm?fobjectid=45084| archive-date = 2009-12-23| url-status = dead}}{{cite web| url =http://exploration.esa.int/science-e/www/object/index.cfm?fobjectid=45103| title = The ExoMars instrument suite| publisher = ESA| accessdate = 2010-03-12}} such an iron-55 source for its combined X-ray diffraction/X-ray fluorescence spectrometer.{{cite conference|title = An European XRD/XRF Instrument for the ExoMars Mission|journal=Lunar and Planetary Science Conference |issue=1338 |author1=Marinangeli, L. |author2=Hutchinson, I. |author3=Baliva, A. |author4=Stevoli, A. |author5=Ambrosi, R. |author6=Critani, F. |author7=Delhez, R. |author8=Scandelli, L. |author9=Holland, A. |author10=Nelms, N. |author11=Mars-Xrd Team |conference= 38th Lunar and Planetary Science Conference|date= March 12–16, 2007|place = League City, Texas|page = 1322|bibcode=2007LPI....38.1322M }} The 2011 Mars mission MSL used a functionally similar spectrometer, but with a traditional, electrically powered X-ray source.[https://web.archive.org/web/20090320125601/http://msl-scicorner.jpl.nasa.gov/Instruments/CheMin/ Chemistry & Mineralogy (CheMin)], NASA

The Auger electrons can be applied in electron capture detectors for gas chromatography. The more widely used nickel-63 sources provide electrons from beta decay.{{cite journal|doi =10.1016/S0021-9673(00)89896-9|title =Iron-55 as an auger electron emitter : Novel source for gas chromatography detectors|author1=D.J. Dwight |author2=E.A. Lorch |author3=J.E. Lovelock | journal = Journal of Chromatography A|volume =116 |year = 1976|issue =2 | pages = 257–261 |url-access=subscription |url=https://www.sciencedirect.com/science/article/abs/pii/S0021967300898969 }}

Iron-55 is most effectively produced by irradiation of iron with neutrons. The reaction (⁵⁴Fe(n,γ)⁵⁵Fe and ⁵⁶Fe(n,2n)⁵⁵Fe) of the two most abundant isotopes iron-54 and iron-56 with neutrons yields iron-55. Most of the observed iron-55 is produced in these irradiation reactions, and it is not a primary fission product.{{cite journal|title = Concentrations of iron-55 in commercial fish species from the North Atlantic| year = 1970| doi =10.1007/BF00353667|last1 = Preston|first1 = A.|journal = Marine Biology|volume = 6|pages = 345–349|issue = 4| s2cid = 91254200}}

As a result of atmospheric nuclear tests in the 1950s, and until the test ban in 1963, considerable amounts of iron-55 have been released into the biosphere.{{cite journal|title = Iron-55 in Humans and Their Foods| year = 1965| doi = 10.1126/science.149.3682.431|last1 = Palmer|first1 = H. E.|last2 = Beasley|first2 = T. M.|journal = Science|volume = 149|pages = 431–2|pmid = 17809410|issue = 3682|bibcode = 1965Sci...149..431P | s2cid = 206565239}} People close to the test ranges, for example Iñupiat (Alaska Natives) and inhabitants of the Marshall Islands, accumulated significant amounts of radioactive iron. However, the short half-life and the test ban decreased, within several years, the available amount of iron-55 nearly to the pre-nuclear test levels.{{cite journal|title =Iron-55 in Rongelap people, fish and soils|year = 1965| doi =10.1097/00004032-197203000-00005|last3 = Conard|first3 = R. M.E.|last2 = Held|first2 = E. E.|last1 = Beasley|first1 = T. M.|journal = Health Physics|volume = 22|pages = 245–50|pmid = 5062744|issue = 3 }}

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• Isotopes of iron

Category:Isotopes of iron