Iron-55

Properties and data of the isotope ⁵⁵Fe.

Content

General Data

Radioactive Decay

Parent Nuclides

Formation

Isotones und Isobares

Literature

Iron-55 is a radioisotope of the chemical element iron, which, in addition to the element-specific 26 protons, has 29 neutrons in the atomic nucleus, resulting in the mass number 55.

General data

Name of the isotope:Iron-55; Fe-55Symbol:⁵⁵Fe or 5526FeMass number A:55 (= number of nucleons)Atomic number Z:26 (= number of protons)Neutrons N:29Isotopic mass:54.9382912(3) u (atomic weight of Iron-55)Nuclide mass:54.9240285 u (calculated nuclear mass without electrons)Mass excess:-57.48138 MeVMass defect:0.516442196 u (per nucleus)Nuclear binding energy:481.06280692 MeV (per nucleus)
8.74659649 MeV (average binding energy per nucleon)Separation energy:S_N = 9.29812(19) MeV (first neutron)
S_P = 9.2121(10) MeV (first proton)Half-life:2.744(9) aDecay constant λ:8.010041147845 × 10^-9 s^-1Specific activity α:89328881641142 Bq g^-1
2414.2940984092 Ci g^-1Spin and parity:
(nuclear angular momentum)3/2-Mirror nucleus:Copper-55Year of discovery:1939

Radioactive Decay

A more recent value for the half-life of iron-55 was published in 2019: 1006.70(15) days or 2.7563(4) years [2].

Half-life T_½ = 2.744(9) a respectively 8.6534784 × 10⁷ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EE	⁵⁵Mn	100 %	0.2311(4) MeV

Parent Nuclides

Direct parent isotope is: ⁵⁵Co.

Formation

⁵⁵Fe can be artificially produced by neutron irradiation of stable iron isotopes: ⁵⁴Fe(n,γ)⁵⁵Fe or ^{56Fe(n,2n)⁵⁵Fe. Accordingly, iron-containing components such as steel or reinforced concrete that are exposed to neutron radiation can accumulate with Fe-55.}

Significant amounts of iron-55 were also released by atmospheric nuclear weapons tests in the 1950s [1].

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 29) and isobaric (same nucleon number A = 55) with Iron-55. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 29	Isobar A = 55
13	⁴²Al
14	⁴³Si
15	⁴⁴P
16	⁴⁵S
17	⁴⁶Cl
18	⁴⁷Ar
19	⁴⁸K	⁵⁵K
20	⁴⁹Ca	⁵⁵Ca
21	⁵⁰Sc	⁵⁵Sc
22	⁵¹Ti	⁵⁵Ti
23	⁵²V	⁵⁵V
24	⁵³Cr	⁵⁵Cr
25	⁵⁴Mn	⁵⁵Mn
26	⁵⁵Fe	⁵⁵Fe
27	⁵⁶Co	⁵⁵Co
28	⁵⁷Ni	⁵⁵Ni
29	⁵⁸Cu	⁵⁵Cu
30	⁵⁹Zn	⁵⁵Zn
31	⁶⁰Ga
32	⁶¹Ge
33	⁶²As
34	⁶³Se

External data and identifiers

CAS:14681-59-5InChI Key:XEEYBQQBJWHFJM-BJUDXGSMSA-NSMILES:[55Fe]PubChem:ID 26815Adopted Levels, Gammas:NuDat 55Fe

Literature and References

[1] - Harvey E. Palmer, Thomas M. Beasley:
Iron-55 in Humans and Their Foods.
In: Science, 149, 3682, 431 - 432, (1965), DOI 10.1126/science.149.3682.431.

[2] - S. Pommé, H. Stroh, R. Van Ammel:
The ⁵⁵Fe half-life measured with a pressurised proportional counter.
In: Applied Radiation and Isotopes, 148, 27-34, (2019), DOI 10.1016/j.apradiso.2019.01.008.