Editing Einsteinium (section)

==Synthesis and extraction==
[[File:EsProduction.png|thumb|upright=1.4|Early evolution of einsteinium production in the U.S.<ref name="s51">[[#Seaborg|Seaborg]], p. 51</ref>]]
Einsteinium is produced in minute quantities by bombarding lighter actinides with neutrons in dedicated high-flux [[nuclear reactor]]s. The world's major irradiation sources are the 85-megawatt [[High Flux Isotope Reactor]] (HFIR) at [[Oak Ridge National Laboratory]] (ORNL), Tennessee, U.S.,<ref>{{cite web|title = High Flux Isotope Reactor|url = http://neutrons.ornl.gov/facilities/HFIR/|publisher = Oak Ridge National Laboratory|access-date = 2010-09-23|archive-date = 2015-02-28|archive-url = https://web.archive.org/web/20150228152355/http://neutrons.ornl.gov/facilities/HFIR/|url-status = live}}</ref> and the SM-2 loop reactor at the [[Research Institute of Atomic Reactors]] (NIIAR) in [[Dimitrovgrad, Russia]],<ref>{{cite web|script-title = ru:Радионуклидные источники и препараты|url = http://www.niiar.ru/?q=radioisotope_application|publisher = Research Institute of Atomic Reactors|access-date = 2010-09-26|language = ru|archive-date = 2020-07-26|archive-url = https://web.archive.org/web/20200726202716/http://www.niiar.ru/?q=radioisotope_application|url-status = live}}</ref> which are both dedicated to the production of transcurium (''Z''>96) elements. These facilities have similar power and flux levels, and are expected to have comparable production capacities for transcurium elements,<ref name="h1582">[[#Haire|Haire]], p. 1582</ref> though the quantities produced at NIIAR are not widely reported. In a "typical processing campaign" at ORNL, tens of grams of [[curium]] are irradiated to produce decigram quantities of [[californium]], milligrams of berkelium ({{sup|249}}Bk) and einsteinium and picograms of [[fermium]].<ref>[[#Greenwood|Greenwood]], p. 1262</ref><ref>{{cite journal|first1 = C. E.|last1 = Porter|first2 = F. D. Jr. |last2 = Riley|first3 = R. D.|last3 = Vandergrift|first4 = L. K.|last4 = Felker|title = Fermium Purification Using Teva Resin Extraction Chromatography|journal = Sep. Sci. Technol.|volume = 32|issue = 1–4|date = 1997|pages = 83–92|doi = 10.1080/01496399708003188|url = https://zenodo.org/record/1234415|access-date = 2018-05-18|archive-date = 2020-03-11|archive-url = https://web.archive.org/web/20200311030820/https://zenodo.org/record/1234415|url-status = live}}</ref>

The first microscopic sample of {{sup|253}}Es sample weighing about 10 [[nanogram]]s was prepared in 1961 at HFIR. A special magnetic balance was designed to estimate its weight.<ref name="CRC" /><ref>Hoffman, Darleane C.; Ghiorso, Albert and Seaborg, Glenn Theodore (2000) ''The Transuranium People: The Inside Story'', Imperial College Press, pp.&nbsp;190–191, {{ISBN|978-1-86094-087-3}}.</ref> Larger batches were produced later starting from several kilograms of plutonium with the einsteinium yields (mostly {{sup|253}}Es) of 0.48 milligram in 1967–1970, 3.2 milligrams in 1971–1973, followed by steady production of about 3 milligrams per year between 1974 and 1978.<ref name="s36">[[#Seaborg|Seaborg]], pp. 36–37</ref> These quantities however refer to the integral amount in the target right after irradiation. Subsequent separation procedures reduced the amount of isotopically pure einsteinium roughly tenfold.<ref name="h1582" />

===Laboratory synthesis===
Heavy neutron irradiation of plutonium results in four major isotopes of einsteinium: {{sup|253}}Es (α-emitter; half-life 20.47 days, spontaneous fission half-life 7×10{{sup|5}} years); {{sup|254m}}Es (β-emitter, half-life 39.3 hours), {{sup|254}}Es (α-emitter, half-life 276 days) and {{sup|255}}Es (β-emitter, half-life 39.8 days).<ref>{{cite journal|last1=Jones|first1=M.|last2=Schuman|first2=R.|last3=Butler|first3=J.|last4=Cowper|first4=G.|last5=Eastwood|first5=T.|last6=Jackson|first6=H.|title=Isotopes of Einsteinium and Fermium Produced by Neutron Irradiation of Plutonium|journal=Physical Review|volume=102|issue=1|pages=203–207|date=1956|doi=10.1103/PhysRev.102.203|bibcode = 1956PhRv..102..203J }}</ref>{{NUBASE2016|ref}} An alternative route involves bombardment of uranium-238 with high-intensity nitrogen or oxygen ion beams.<ref>{{cite journal|last1=Guseva|first1=L.|last2=Filippova|first2=K.|last3=Gerlit|first3=Y.|last4=Druin|first4=V.|last5=Myasoedov|first5=B.|last6=Tarantin|first6=N.|title=Experiments on the production of einsteinium and fermium with a cyclotron|journal=Journal of Nuclear Energy|volume=3|pages=341–346|date=1956|doi=10.1016/0891-3919(56)90064-X|issue=4}}</ref>

{{sup|247}}Es (half-life 4.55 min) was produced by irradiating {{sup|241}}Am with carbon or {{sup|238}}U with nitrogen ions.<ref name="Binder">Harry H. Binder: ''Lexikon der chemischen Elemente'', S. Hirzel Verlag, Stuttgart 1999, {{ISBN|3-7776-0736-3}}, pp. 18–23.</ref> The latter reaction was first realized in 1967 in Dubna, Russia, and the involved scientists were awarded the [[Lenin Komsomol Prize]].<ref>[http://n-t.ru/ri/ps/pb099.htm Эйнштейний] {{Webarchive|url=https://web.archive.org/web/20210519093938/http://n-t.ru/ri/ps/pb099.htm |date=2021-05-19 }} (in Russian, a popular article by one of the involved scientists)</ref>

{{sup|248}}Es was produced by irradiating {{sup|249}}Cf with [[deuterium]] ions. It mainly β-decays  to {{sup|248}}Cf with a half-life of {{val|25|5}} minutes, but also releases 6.87-MeV α-particles; the ratio of β's to α-particles is about 400.<ref>{{cite journal|last1=Chetham-Strode|first1=A.|last2=Holm|first2=L.|title=New Isotope Einsteinium-248|journal=Physical Review|volume=104|pages=1314|date=1956|doi=10.1103/PhysRev.104.1314|issue=5|bibcode = 1956PhRv..104.1314C |s2cid=102836584 }}</ref>
:<math chem>\ce{^{249}_{98}Cf + ^{2}_{1}H -> ^{248}_{99}Es + 3^{1}_{0}n} \quad \left( \ce{^{248}_{99}Es ->[\epsilon][27 \ce{min}] ^{248}_{98}Cf} \right)</math>

{{sup|249, 250, 251, 252}}Es were obtained by bombarding {{sup|249}}Bk with α-particles. One to four neutrons are released, so four different isotopes are formed in one reaction.<ref>{{cite journal|last1=Harvey|first1=Bernard|last2=Chetham-Strode|first2=Alfred|last3=Ghiorso|first3=Albert|last4=Choppin|first4=Gregory|last5=Thompson|first5=Stanley|title=New Isotopes of Einsteinium|journal=Physical Review|volume=104|pages=1315–1319|date=1956|doi=10.1103/PhysRev.104.1315|issue=5|bibcode=1956PhRv..104.1315H|url=http://www.escholarship.org/uc/item/462945g3|access-date=2019-07-14|archive-date=2020-03-12|archive-url=https://web.archive.org/web/20200312004201/https://escholarship.org/uc/item/462945g3|url-status=live}}</ref>
:<chem>^{249}_{97}Bk ->[+\alpha] ^{249,250,251,252}_{99}Es</chem>

{{sup|253}}Es was produced by irradiating a 0.1–0.2 milligram {{sup|252}}Cf target with a [[thermal neutron]] flux of (2–5)×10{{sup|14}} neutrons/(cm{{sup|2}}·s) for 500–900 hours:<ref>{{cite journal|last1=Kulyukhin|first1=S.|title=Production of microgram quantities of einsteinium-253 by the reactor irradiation of californium|journal=Inorganica Chimica Acta|volume=110|pages=25–26|date=1985|doi=10.1016/S0020-1693(00)81347-X|last2=Auerman|first2=L. N.|last3=Novichenko|first3=V. L.|last4=Mikheev|first4=N. B.|last5=Rumer|first5=I. A.|last6=Kamenskaya|first6=A. N.|last7=Goncharov|first7=L. A.|last8=Smirnov|first8=A. I.}}</ref>
:<chem>^{252}_{98}Cf ->[\ce{(n,\gamma)}] ^{253}_{98}Cf ->[\beta^-][17.81 \ce{d}] ^{253}_{99}Es</chem>

In 2020, scientists at ORNL created about 200 nanograms of {{sup|254}}Es; allowing some chemical properties of the element to be studied for the first time.<ref>{{cite journal|title=Structural and spectroscopic characterization of an einsteinium complex|date=3 February 2021|access-date=3 February 2021|url=https://www.nature.com/articles/s41586-020-03179-3|journal=Nature|volume=590|pages=85–88|doi=10.1038/s41586-020-03179-3|first1=Korey P.|last1=Carter|first2=Katherine M.|last2=Shield|first3=Kurt F.|last3=Smith|first4=Zachary R.|last4=Jones|first5=Jennifer N.|last5=Wacker|first6=Leticia|last6=Arnedo-Sanchez|first7=Tracy M.|last7=Mattox|first8=Liane M.|last8=Moreau|first9=Karah E.|last9=Knope|first10=Stosh A.|last10=Kozimor|first11=Corwin H.|last11=Booth|first12=Rebecca J.|last12=Abergel|issue=7844|pmid=33536647|bibcode=2021Natur.590...85C|osti=1777970 |s2cid=231805413|archive-date=3 February 2021|archive-url=https://web.archive.org/web/20210203162013/https://www.nature.com/articles/s41586-020-03179-3|url-status=live}}</ref>

===Synthesis in nuclear explosions===
[[File:ActinideExplosionSynthesis.png|thumb|upright=1.4|left|Estimated yield of transuranium elements in the U.S. nuclear tests Hutch and Cyclamen<ref name="s40" />]]
The analysis of the debris at the 10-[[TNT equivalent|megaton]] ''Ivy Mike'' nuclear test was a part of long-term project. One of the goals was studying the efficiency of production of transuranic elements in high-power nuclear explosions. The motive for these experiments was that synthesis of such elements from uranium requires multiple neutron capture. The probability of such events increases with the [[neutron flux]], and nuclear explosions are the most powerful man-made neutron sources, providing densities of the order 10{{sup|23}} neutrons/cm{{sup|2}} within a microsecond, or about 10{{sup|29}} neutrons/(cm{{sup|2}}·s). In comparison, the flux of HFIR is 5{{e|15}} neutrons/(cm{{sup|2}}·s). A dedicated laboratory was set up right at [[Enewetak Atoll]] for preliminary analysis of debris, as some isotopes could have decayed by the time the debris samples reached the mainland U.S. The laboratory was receiving samples for analysis as soon as possible, from airplanes equipped with paper filters which flew over the atoll after the tests. Whereas it was hoped to discover new chemical elements heavier than fermium, none of these were found even after a series of megaton explosions conducted between 1954 and 1956 at the atoll.<ref name="s39" />

The atmospheric results were supplemented by the underground test data accumulated in the 1960s at the [[Nevada Test Site]], as it was hoped that powerful explosions in a confined space might give improved yields and heavier isotopes. Apart from traditional uranium charges, combinations of uranium with americium and [[thorium]] have been tried, as well as a mixed plutonium-neptunium charge, but they were less successful in terms of yield and was attributed to stronger losses of heavy isotopes due to enhanced fission rates in heavy-element charges. Product isolation was problematic as the explosions were spreading debris through melting and vaporizing the surrounding rocks at depths of 300–600 meters. Drilling to such depths to extract the products was both slow and inefficient in terms of collected volumes.<ref name="s39" /><ref name="s40">[[#Seaborg|Seaborg]], p. 40</ref>

Of the nine underground tests between 1962 and 1969,<ref>These were codenamed: "Anacostia" (5.2 [[TNT equivalent|kilotons]], 1962), "Kennebec" (<5 kilotons, 1963), "Par" (38 kilotons, 1964), "Barbel" (<20 kilotons, 1964), "Tweed" (<20 kilotons, 1965), "Cyclamen" (13 kilotons, 1966), "Kankakee" (20-200 kilotons, 1966), "Vulcan" (25 kilotons, 1966) and "Hutch" (20-200 kilotons, 1969)</ref><ref>[http://www.nv.doe.gov/library/publications/historical/DOENV_209_REV15.pdf United States Nuclear Tests July 1945 through September 1992] {{webarchive |url=https://web.archive.org/web/20100615231826/http://www.nv.doe.gov/library/publications/historical/DOENV_209_REV15.pdf |date=June 15, 2010 }}, DOE/NV--209-REV 15, December 2000.</ref> the last one was the most powerful and had the highest yield of transuranics. Milligrams of einsteinium that would normally take a year of irradiation in a high-power reactor, were produced within a microsecond.<ref name="s40" /> However, the major practical problem of the entire proposal was collecting the radioactive debris dispersed by the powerful blast. Aircraft filters adsorbed only ~4{{e|-14}} of the total amount, and collection of tons of corals at Enewetak Atoll increased this fraction by only two orders of magnitude. Extraction of about 500 kilograms of underground rocks 60 days after the Hutch explosion recovered only ~1{{e|-7}} of the total charge. The amount of transuranic elements in this 500-kg batch was only 30 times higher than in a 0.4-kg rock picked up 7 days after the test which showed the highly non-linear dependence of the transuranics yield on the amount of retrieved radioactive rock.<ref name="s43">[[#Seaborg|Seaborg]], p. 43</ref> Shafts were drilled at the site before the test in order to accelerate sample collection after explosion, so that explosion would expel radioactive material from the epicenter through the shafts and to collecting volumes near the surface. This method was tried in two tests and instantly provided hundreds of kilograms of material, but with actinide concentration 3 times lower than in samples obtained after drilling. Whereas such method could have been efficient in scientific studies of short-lived isotopes, it could not improve the overall collection efficiency of the produced actinides.<ref name="s44">[[#Seaborg|Seaborg]], p. 44</ref>

Though no new elements (except einsteinium and fermium) could be detected in the nuclear test debris, and the total yields of transuranics were disappointingly low, these tests did provide significantly higher amounts of rare heavy isotopes than previously available in laboratories.<!-- About 6E9 atoms of 257Fm could be recovered after the Hutch detonation. These were then used in the studies of thermal-neutron induced fission of 257Fm, and in discovery of a new nuclide, 258Fm. Also, the rare 250Cm isotope was synthesized in large quantities, which is very hard to produce in nuclear reactors from its progenitor 249Cm: 249Cm's half-life (64 minutes) is much too short for months-long reactor irradiation, but very "long" on the timescale of an explosion.--><ref name="s47">[[#Seaborg|Seaborg]], p. 47</ref>

===Separation===
[[File:Elutionskurven Fm Es Cf Bk Cm Am.png|thumb|[[Elution]] curves: chromatographic separation of Fm(100), Es(99), Cf, Bk, Cm and Am]]
Separation procedure of einsteinium depends on the synthesis method. In the case of light-ion bombardment inside a cyclotron, the heavy ion target is attached to a thin foil, and the generated einsteinium is simply washed off the foil after the irradiation. However, the produced amounts in such experiments are relatively low.<ref name="h1583">[[#Haire|Haire]], p. 1583</ref> The yields are much higher for reactor irradiation, but there, the product is a mixture of various actinide isotopes, as well as lanthanides produced in the nuclear fission decays. In this case, isolation of einsteinium is a tedious procedure which involves several repeating steps of cation exchange, at elevated temperature and pressure, and chromatography. Separation from berkelium is important, because the most common einsteinium isotope produced in nuclear reactors, {{sup|253}}Es, decays with a half-life of only 20 days to {{sup|249}}Bk, which is fast on the timescale of most experiments. Such separation relies on the fact that berkelium easily oxidizes to the solid +4 state and precipitates, whereas other actinides, including einsteinium, remain in their +3 state in solutions.<ref name="h1584">[[#Haire|Haire]], pp. 1584–1585</ref>

Trivalent actinides can be separated from lanthanide fission products by a cation-exchange resin column using a 90% water/10% ethanol solution saturated with [[hydrochloric acid]] (HCl) as [[eluant]]. It is usually followed by [[anion-exchange chromatography]] using 6 [[molar concentration|molar]] HCl as eluant. A cation-exchange resin column (Dowex-50 exchange column) treated with ammonium salts is then used to separate fractions containing elements 99, 100 and 101. These elements can be then identified simply based on their elution position/time, using α-hydroxyisobutyrate solution (α-HIB), for example, as eluant.<ref name="book2">{{cite book|url=https://books.google.com/books?id=U4rnzH9QbT4C&pg=PA11|pages=9–11|title=The new chemistry|author=Hall, Nina|publisher=Cambridge University Press|date=2000|isbn=978-0-521-45224-3|access-date=2016-01-05|archive-date=2016-05-20|archive-url=https://web.archive.org/web/20160520024221/https://books.google.com/books?id=U4rnzH9QbT4C&pg=PA11|url-status=live}}</ref>

The 3+ actinides can also be separated via solvent extraction chromatography, using bis-(2-ethylhexyl) phosphoric acid (abbreviated as HDEHP) as the stationary organic phase, and nitric acid as the mobile aqueous phase. The actinide elution sequence is reversed from that of the cation-exchange resin column. The einsteinium separated by this method has the advantage to be free of organic complexing agent, as compared to the separation using a resin column.<ref name="book2" />

===Preparation of the metal===
Einsteinium is highly reactive, so strong reducing agents are required to obtain the pure metal from its compounds.<ref name="h1588">[[#Haire|Haire]], p. 1588</ref> This can be achieved by reduction of [[einsteinium(III) fluoride]] with metallic [[lithium]]:
:EsF{{sub|3}} + 3 Li → Es + 3 LiF

However, owing to its low melting point and high rate of self-radiation damage, einsteinium has a higher vapor pressure than [[lithium fluoride]]. This makes this reduction reaction rather inefficient. It was tried in the early preparation attempts and quickly abandoned in favor of reduction of einsteinium(III) oxide with [[lanthanum]] metal:<ref name="ev">{{cite journal|last1=Haire|first1=R.|title=Preparation, properties, and some recent studies of the actinide metals|url=http://www.osti.gov/bridge/product.biblio.jsp?osti_id=5235830|doi=10.1016/0022-5088(86)90554-0|date=1986|pages=379–398|volume=121|journal=Journal of the Less Common Metals|s2cid=97518446 |access-date=2010-11-24|archive-date=2013-05-13|archive-url=https://web.archive.org/web/20130513130241/http://www.osti.gov/bridge/product.biblio.jsp?osti_id=5235830|url-status=live}}</ref><ref name="ES_METALL" /><ref name="h1590">[[#Haire|Haire]], p. 1590</ref>
:Es{{sub|2}}O{{sub|3}} + 2 La → 2 Es + La{{sub|2}}O{{sub|3}}