Editing Europium (section)

===Isotopes===
{{Main|Isotopes of europium}}
Naturally occurring europium is composed of two [[isotope]]s, <sup>151</sup>Eu and <sup>153</sup>Eu, which occur in almost equal proportions; <sup>153</sup>Eu is slightly more abundant (52.2% [[natural abundance]]). While <sup>153</sup>Eu is stable, <sup>151</sup>Eu was found to be unstable to [[alpha decay]] with a [[half-life]] of {{val|5|+11|-3|e=18|ul=years}} in 2007,<ref>{{cite journal|title=Search for α decay of natural europium|author= Belli, P.|doi=10.1016/j.nuclphysa.2007.03.001|date=2007|journal=Nuclear Physics A|volume=789|issue= 1|pages=15–29|display-authors=1|last2=Bernabei|first2=R.|last3=Cappella|first3=F.|last4=Cerulli|first4=R.|last5=Dai|first5=C.|last6=Danevich|first6=F.|last7=Dangelo|first7=A.|last8=Incicchitti|first8=A.|last9=Kobychev|first9=V.|last10= Nagorny|first10= S. S.|last11= Nisi|first11= S.|last12= Nozzoli|first12= F.|last13= Prosperi|first13= D.|last14= Tretyak|first14= V. I.|last15= Yurchenko|first15= S. S.|bibcode = 2007NuPhA.789...15B }}</ref> giving about one alpha decay per two minutes in every kilogram of natural europium. This value is in reasonable agreement with theoretical predictions. Besides the natural radioisotope <sup>151</sup>Eu, 35 artificial radioisotopes have been characterized, the most stable being <sup>150</sup>Eu with a half-life of 36.9 years, <sup>152</sup>Eu with a half-life of 13.516 years, and <sup>154</sup>Eu with a half-life of 8.593 years. All the remaining [[radioactive]] isotopes have half-lives shorter than 4.7612 years, and the majority of these have half-lives shorter than 12.2 seconds; the known isotopes of europium range from <sup>130</sup>Eu to <sup>170</sup>Eu.<ref name=Ln922>{{cite journal |last1=Kiss |first1=G. G. |last2=Vitéz-Sveiczer |first2=A. |last3=Saito |first3=Y. |display-authors=et al. |title=Measuring the β-decay properties of neutron-rich exotic Pm, Sm, Eu, and Gd isotopes to constrain the nucleosynthesis yields in the rare-earth region |journal=The Astrophysical Journal |volume=936 |issue=107 |date=2022 |page=107 |doi=10.3847/1538-4357/ac80fc|bibcode=2022ApJ...936..107K |s2cid=252108123 |hdl=2117/375253 |hdl-access=free |doi-access=free }}</ref>{{NUBASE2020|ref}} This element also has 17 [[meta state]]s, with the most stable being <sup>150m</sup>Eu (''t''<sub>1/2</sub>=12.8 hours), <sup>152m1</sup>Eu (''t''<sub>1/2</sub>=9.3116 hours) and <sup>152m2</sup>Eu (''t''<sub>1/2</sub>=96 minutes).{{NUBASE2020|ref}}<ref name="nucleonica">{{cite web |url=http://www.nucleonica.net/unc.aspx |title=Nucleonica: Universal Nuclide Chart |author=Nucleonica |date=2007–2011 |publisher=Nucleonica |access-date=July 22, 2011}}</ref>

The primary [[decay mode]] for isotopes lighter than <sup>153</sup>Eu is [[electron capture]], and the primary mode for heavier isotopes is [[beta minus decay]]. The primary [[decay product]]s before <sup>153</sup>Eu are isotopes of [[samarium]] (Sm) and the primary products after are isotopes of [[gadolinium]] (Gd).<ref name="nucleonica" />

====Europium as a nuclear fission product====
{{Medium-lived fission products}}
Europium is produced by nuclear fission; 
[[Europium-155|<sup>155</sup>Eu]] (half-life 4.7612 years) has a fission yield of 330 parts per million (ppm) for [[uranium-235]] and [[thermal neutron]]s.<ref>{{cite journal |last1=Aarkrog |first1=A. |last2=Lippert |first2=J. |title=Europium-155 in Debris from Nuclear Weapons |journal=Science |date=28 July 1967 |volume=157 |issue=3787 |pages=425–427 |doi=10.1126/science.157.3787.425 |pmid=6028023 |bibcode=1967Sci...157..425A }}</ref>
The [[fission product yield]]s of europium isotopes are low near the top of the mass range for [[fission products]].

As with other lanthanides, many isotopes of europium, especially those that have odd mass numbers or are neutron-poor like <sup>152</sup>Eu, have high [[Neutron cross-section|cross section]]s for [[neutron capture]], often high enough to be [[neutron poison]]s.
<div style="float:left; margin:0.25em">
{| class="wikitable" align="right" style="margin:1em"
|+ Thermal neutron capture cross sections
!Isotope
|<sup>151</sup>Eu||<sup>152</sup>Eu||<sup>153</sup>Eu||<sup>154</sup>Eu||<sup>155</sup>Eu
|-
!Yield
|~10||low||1580||>2.5||330
|-
!Barns
|5900||12800||312||1340||3950
|}
</div>
<sup>151</sup>Eu is the [[beta decay]] product of [[samarium-151]], but since this has a long decay half-life and short mean time to neutron absorption, most <sup>151</sup>Sm instead ends up as <sup>152</sup>Sm.

<sup>152</sup>Eu (half-life 13.516 years) and <sup>154</sup>Eu (half-life 8.593 years) cannot be beta decay products because <sup>152</sup>Sm and <sup>154</sup>Sm are non-radioactive, but <sup>154</sup>Eu is the only long-lived "shielded" [[nuclide]], other than [[Caesium-134|<sup>134</sup>Cs]], to have a fission yield of more than 2.5 [[parts per million]] fissions.<ref>[http://wwwndc.jaea.go.jp/NuC/index.html Tables of Nuclear Data], Japan Atomic Energy Agency {{webarchive |url=https://web.archive.org/web/20150610213313/http://wwwndc.jaea.go.jp/NuC/index.html |date=June 10, 2015 }}</ref> A larger amount of <sup>154</sup>Eu is produced by [[neutron activation]] of a significant portion of the non-radioactive <sup>153</sup>Eu; however, much of this is further converted to <sup>155</sup>Eu.