Editing Promethium (section)

==Occurrence==
[[File:Pitchblende schlema-alberoda.JPG|left|thumb|[[Uraninite]], a uranium ore and the host for most of Earth's promethium ]]
In 1934, [[Willard Libby]] reported that he had found weak beta activity in pure neodymium, which was attributed to a half-life over 10<sup>12</sup>&nbsp;years.{{sfn|Lavrukhina|Pozdnyakov|1966|p=117}} Almost 20 years later, it was claimed that the element occurs in natural neodymium in equilibrium in quantities below 10<sup>−20</sup> grams of promethium per one gram of neodymium.{{sfn|Lavrukhina|Pozdnyakov|1966|p=117}} However, these observations were disproved by newer investigations, because for all seven naturally occurring neodymium isotopes, any single beta decays (which can produce promethium isotopes) are forbidden by energy conservation.<ref>{{cite journal |author1=G. Audi |author2=A. H. Wapstra |author3=C. Thibault |author4=J. Blachot |author5=O. Bersillon |year=2003 |title=The NUBASE evaluation of nuclear and decay properties |url=http://www.nndc.bnl.gov/amdc/nubase/Nubase2003.pdf |journal=[[Nuclear Physics A]] |volume=729 |issue=1 |pages=3–128 |doi=10.1016/j.nuclphysa.2003.11.001 |bibcode=2003NuPhA.729....3A |url-status=dead |archive-url=https://web.archive.org/web/20080923135135/http://www.nndc.bnl.gov/amdc/nubase/Nubase2003.pdf |archive-date=2008-09-23 |citeseerx=10.1.1.692.8504 }}</ref> In particular, careful measurements of atomic masses show that the mass difference between <sup>150</sup>Nd and <sup>150</sup>Pm is negative (−87&nbsp;keV), which absolutely prevents the single beta decay of <sup>150</sup>Nd to <sup>150</sup>Pm.<ref>{{cite book |author=N. E. Holden |year=2004 |editor=D. R. Lide |chapter=Table of the Isotopes |title=CRC Handbook of Chemistry and Physics |page=[https://archive.org/details/crchandbookofche81lide/page/ Section 11] |no-pp=yes |edition=85th |publisher=[[CRC Press]] |isbn=978-0-8493-0485-9 |title-link=CRC Handbook of Chemistry and Physics }}</ref>

In 1965, [[Olavi Erämetsä]] separated out traces of <sup>147</sup>Pm from a rare earth concentrate purified from [[apatite]], resulting in an upper limit of 10<sup>−21</sup> for the abundance of promethium in nature; this may have been produced by the natural nuclear fission of uranium, or by [[cosmic ray spallation]] of <sup>146</sup>Nd.<ref>{{Ullmann|volume=31|page=188|last1=McGill|first1=Ian|contribution=Rare Earth Elements|doi=10.1002/14356007.a22_607}}</ref>

Both isotopes of natural europium have larger [[mass excess]]es than sums of those of their potential alpha daughters plus that of an alpha particle; therefore, they (stable in practice) may alpha decay to promethium.<ref name="Mammamia" /> Research at [[Laboratori Nazionali del Gran Sasso]] showed that europium-151 decays to promethium-147 with the half-life of 5{{e|18}}&nbsp;years;<ref name="Mammamia" /> later measurements gave the half-life as (4.62&nbsp;±&nbsp;0.95(stat.)&nbsp;±&nbsp;0.68(syst.))&nbsp;×&nbsp;10<sup>18</sup> years.<ref>
{{cite journal
 |first1=N.|last1=Casali |first2=S. S. |last2=Nagorny |first3=F. |last3=Orio |first4=L. |last4=Pattavina |year=2014
 |title=Discovery of the <sup>151</sup>Eu α decay
 |journal=[[Journal of Physics G: Nuclear and Particle Physics]]
 |volume=41 |number=7 |pages=075101
 |doi=10.1088/0954-3899/41/7/075101 |display-authors=etal|arxiv=1311.2834|bibcode=2014JPhG...41g5101C|s2cid=116920467 }}</ref> It has been shown that europium is "responsible" for about 12&nbsp;grams of promethium in the Earth's crust.<ref name="Mammamia" /> Alpha decays for europium-153 have not been found yet, and its theoretically calculated half-life is so high (due to low energy of decay) that this process will probably not be observed in the near future.<ref name="bellidecay">{{cite journal |last1=Belli |first1=P. |last2=Bernabei |first2=R. |last3=Danevich |first3=F. A. |last4=Incicchitti |first4=A. |last5=Tretyak |first5=V. I. |display-authors=3 |title=Experimental searches for rare alpha and beta decays |journal=European Physical Journal A |date=2019 |volume=55 |issue=8 |pages=140–1–140–7 |doi=10.1140/epja/i2019-12823-2 |issn=1434-601X |arxiv=1908.11458|bibcode=2019EPJA...55..140B |s2cid=201664098 }}</ref>

Promethium can also be formed in nature as a product of [[spontaneous fission]] of [[uranium-238]].{{sfn|Lavrukhina|Pozdnyakov|1966|p=117}} Only trace amounts can be found in naturally occurring ores: a sample of [[pitchblende]] has been found to contain promethium at a concentration of four parts per quintillion (4{{e|-18}}) by mass.<ref>{{cite journal |author1=Attrep, Moses Jr. |author2=Kuroda, P. K. |name-list-style=amp |date=May 1968 |title=Promethium in pitchblende |journal=Journal of Inorganic and Nuclear Chemistry |volume=30 |issue=3 |pages=699–703 |doi=10.1016/0022-1902(68)80427-0}}</ref> Uranium is thus "responsible" for 560&nbsp;g of promethium in [[Earth's crust]].<ref name="Mammamia">{{cite journal |last1=Belli |first1=P. |last2=Bernabei |first2=R. |last3=Cappella |first3=F. |last4=Cerulli |first4=R. |last5=Dai |first5=C. J. |last6=Danevich |first6=F. A. |last7=D'Angelo |first7=A. |last8=Incicchitti |first8=A. |last9=Kobychev |first9=V. V. |title=Search for α decay of natural Europium |year=2007 |journal=Nuclear Physics A |volume=789 |issue=1–4 |pages=15–29 |doi=10.1016/j.nuclphysa.2007.03.001 |bibcode=2007NuPhA.789...15B |display-authors=3}}</ref>

Promethium has also been identified in the spectrum of the star [[HR 465]] in [[Andromeda (constellation)|Andromeda]]; it also has been found in HD 101065 ([[Przybylski's star]]) and HD 965.<ref>{{cite journal|author1=C. R. Cowley |author2=W. P. Bidelman |author3=S. Hubrig |author4=G. Mathys |author5=D. J. Bord |name-list-style=amp |year = 2004|title = On the possible presence of promethium in the spectra of HD 101065 (Przybylski's star) and HD 965|journal = Astronomy & Astrophysics|volume = 419|pages = 1087–1093|doi = 10.1051/0004-6361:20035726|bibcode=2004A&A...419.1087C|issue = 3|doi-access=free}}</ref> Because of the short half-life of promethium isotopes, they should be formed near the surface of those stars.<ref name="CRCel">{{cite book | editor= Haynes, William M. | year = 2011 | title = CRC Handbook of Chemistry and Physics | edition = 92nd | publisher = [[CRC Press]] | isbn = 978-1439855119|page=4.28|chapter=Prometium in "The Elements"|author=Hammond, C. R.| title-link = CRC Handbook of Chemistry and Physics }}</ref>