======================================================================
= Einsteinium =
======================================================================
Introduction
======================================================================
Einsteinium is a synthetic chemical element; it has symbol Es and
atomic number 99 and is a member of the actinide series and the
seventh transuranium element.
Einsteinium was discovered as a component of the debris of the first
hydrogen bomb explosion in 1952. Its most common isotope,
einsteinium-253 ((253)Es; half-life 20.47 days), is produced
artificially from decay of californium-253 in a few dedicated
high-power nuclear reactors with a total yield on the order of one
milligram per year. The reactor synthesis is followed by a complex
process of separating einsteinium-253 from other actinides and
products of their decay. Other isotopes are synthesized in various
laboratories, but in much smaller amounts, by bombarding heavy
actinide elements with light ions. Due to the small amounts of
einsteinium produced and the short half-life of its most common
isotope, there are no practical applications for it except basic
scientific research. In particular, einsteinium was used to
synthesize, for the first time, 17 atoms of the new element
mendelevium in 1955.
Einsteinium is a soft, silvery, paramagnetic metal. Its chemistry is
typical of the late actinides, with a preponderance of the +3
oxidation state; the +2 oxidation state is also accessible, especially
in solids. The high radioactivity of (253)Es produces a visible glow
and rapidly damages its crystalline metal lattice, with released heat
of about 1000 watts per gram. Studying its properties is difficult due
to (253)Es's decay to berkelium-249 and then californium-249 at a rate
of about 3% per day. The longest-lived isotope of einsteinium, (252)Es
(half-life 471.7 days) would be more suitable for investigation of
physical properties, but it has proven far more difficult to produce
and is available only in minute quantities, not in bulk. Einsteinium
is the element with the highest atomic number which has been observed
in macroscopic quantities in its pure form as einsteinium-253.
Like all synthetic transuranium elements, isotopes of einsteinium are
very radioactive and are considered highly dangerous to health on
ingestion.
History
======================================================================
Einsteinium was first identified in December 1952 by Albert Ghiorso
and co-workers at University of California, Berkeley in collaboration
with the Argonne and Los Alamos National Laboratories, in the fallout
from the 'Ivy Mike' nuclear test. The test was done on November 1,
1952, at Enewetak Atoll in the Pacific Ocean and was the first
successful test of a thermonuclear weapon. Initial examination of the
debris from the explosion had shown the production of a new isotope of
plutonium, , which could only have formed by the absorption of six
neutrons by a uranium-238 nucleus followed by two beta decays.
:^{238}_{92}U ->[\ce{+ 6(n,\gamma)}][-2\ \beta^-]{} ^{244}_{94}Pu
At the time, the multiple neutron absorption was thought to be an
extremely rare process, but the identification of (244)Pu indicated
that still more neutrons could have been captured by the uranium,
producing new elements heavier than californium.
Ghiorso and co-workers analyzed filter papers which had been flown
through the explosion cloud on airplanes (the same sampling technique
that had been used to discover (244)Pu). Larger amounts of radioactive
material were later isolated from coral debris of the atoll, and these
were delivered to the U.S. The separation of suspected new elements
was carried out in the presence of a citric acid/ammonium buffer
solution in a weakly acidic medium (pH ≈ 3.5), using ion exchange at
elevated temperatures; fewer than 200 atoms of einsteinium were
recovered in the end. Nevertheless, element 99, einsteinium, and in
particular (253)Es, could be detected via its characteristic
high-energy alpha decay at 6.6 MeV. It was produced by the capture of
15 neutrons by uranium-238 nuclei followed by seven beta decays, and
had a half-life of 20.5 days. Such multiple neutron absorption was
made possible by the high neutron flux density during the detonation,
so that newly generated heavy isotopes had plenty of available
neutrons to absorb before they could disintegrate into lighter
elements. Neutron capture initially raised the mass number without
changing the atomic number of the nuclide, and the concomitant
beta-decays resulted in a gradual increase in the atomic number:
:
^{238}_{92}U ->[\ce{+15n}][6 \beta^-] ^{253}_{98}Cf ->[\beta^-]
^{253}_{99}Es
Some (238)U atoms, however, could absorb two additional neutrons (for
a total of 17), resulting in (255)Es, as well as in the (255)Fm
isotope of another new element, fermium. The discovery of the new
elements and the associated new data on multiple neutron capture were
initially kept secret on the orders of the U.S. military until 1955
due to Cold War tensions and competition with Soviet Union in nuclear
technologies. However, the rapid capture of so many neutrons would
provide needed direct experimental confirmation of the r-process
multi-neutron absorption needed to explain the cosmic nucleosynthesis
(production) of certain heavy elements (heavier than nickel) in
supernovas, before beta decay. Such a process is needed to explain the
existence of many stable elements in the universe.
Meanwhile, isotopes of element 99 (as well as of new element 100,
fermium) were produced in the Berkeley and Argonne laboratories, in a
nuclear reaction between nitrogen-14 and uranium-238, and later by
intense neutron irradiation of plutonium or californium:
:^{252}_{98}Cf ->[\ce{(n,\gamma)}] ^{253}_{98}Cf
->[\beta^-][17.81 \ce{d}] ^{253}_{99}Es ->[\ce{(n,\gamma)}]
^{254}_{99}Es ->[\beta^-] ^{254}_{100}Fm
These results were published in several articles in 1954 with the
disclaimer that these were not the first studies that had been carried
out on the elements. The Berkeley team also reported some results on
the chemical properties of einsteinium and fermium. The 'Ivy Mike'
results were declassified and published in 1955.
In their discovery of elements 99 and 100, the American teams had
competed with a group at the Nobel Institute for Physics, Stockholm,
Sweden. In late 1953 - early 1954, the Swedish group succeeded in
synthesizing light isotopes of element 100, in particular (250)Fm, by
bombarding uranium with oxygen nuclei. These results were also
published in 1954. Nevertheless, the priority of the Berkeley team was
generally recognized, as its publications preceded the Swedish
article, and they were based on the previously undisclosed results of
the 1952 thermonuclear explosion; thus the Berkeley team was given the
privilege to name the new elements. As the effort which had led to the
design of 'Ivy Mike' was codenamed Project PANDA, element 99 had been
jokingly nicknamed "Pandemonium" but the official names suggested by
the Berkeley group derived from two prominent scientists, Einstein and
Fermi: "We suggest for the name for the element with the atomic number
99, einsteinium (symbol E) after Albert Einstein and for the name for
the element with atomic number 100, fermium (symbol Fm), after Enrico
Fermi." Both Einstein and Fermi died between the time the names were
originally proposed and when they were announced. The discovery of
these new elements was announced by Albert Ghiorso at the first Geneva
Atomic Conference held on 8-20 August 1955. The symbol for einsteinium
was first given as "E" and later changed to "Es" by IUPAC.
Physical
==========
Einsteinium is a synthetic, silvery, radioactive metal. In the
periodic table, it is located to the right of the actinide
californium, to the left of the actinide fermium and below the
lanthanide holmium with which it shares many similarities in physical
and chemical properties. Its density of 8.84 g/cm(3) is lower than
that of californium (15.1 g/cm(3)) and is nearly the same as that of
holmium (8.79 g/cm(3)), despite einsteinium being much heavier per
atom than holmium. Einsteinium's melting point (860 °C) is also
relatively low - below californium (900 °C), fermium (1527 °C) and
holmium (1461 °C). Einsteinium is a soft metal, with a bulk modulus of
only 15 GPa, one of the lowest among non-alkali metals.
Unlike the lighter actinides californium, berkelium, curium and
americium, which crystallize in a double hexagonal structure at
ambient conditions; einsteinium is believed to have a face-centered
cubic ('fcc') symmetry with the space group 'Fm'm' and the lattice
constant . However, there is a report of room-temperature hexagonal
einsteinium metal with and , which converted to the 'fcc' phase upon
heating to 300 °C.
The self-damage induced by the radioactivity of einsteinium is so
strong that it rapidly destroys the crystal lattice, and the energy
release during this process, 1000 watts per gram of 253Es, induces a
visible glow. These processes may contribute to the relatively low
density and melting point of einsteinium. Further, due to the small
size of available samples, the melting point of einsteinium was often
deduced by observing the sample being heated inside an electron
microscope. Thus, surface effects in small samples could reduce the
melting point.
The metal is trivalent and has a noticeably high volatility. In order
to reduce the self-radiation damage, most measurements of solid
einsteinium and its compounds are performed right after thermal
annealing. Also, some compounds are studied under the atmosphere of
the reductant gas, for example HO+HCl for EsOCl so that the sample is
partly regrown during its decomposition.
Apart from the self-destruction of solid einsteinium and its
compounds, other intrinsic difficulties in studying this element
include scarcity - the most common (253)Es isotope is available only
once or twice a year in sub-milligram amounts - and self-contamination
due to rapid conversion of einsteinium to berkelium and then to
californium at a rate of about 3.3% per day:
:
^{253}_{99}Es ->[\alpha][20 \ce{d}] ^{249}_{97}Bk
->[\beta^-][314 \ce{d}] ^{249}_{98}Cf
Thus, most einsteinium samples are contaminated, and their intrinsic
properties are often deduced by extrapolating back experimental data
accumulated over time. Other experimental techniques to circumvent the
contamination problem include selective optical excitation of
einsteinium ions by a tunable laser, such as in studying its
luminescence properties.
Magnetic properties have been studied for einsteinium metal, its oxide
and fluoride. All three materials showed Curie-Weiss paramagnetic
behavior from liquid helium to room temperature. The effective
magnetic moments were deduced as for EsO and for the EsF, which are
the highest values among actinides, and the corresponding Curie
temperatures are 53 and 37 K.
Chemical
==========
Like all actinides, einsteinium is rather reactive. Its trivalent
oxidation state is most stable in solids and aqueous solution where it
induces a pale pink color. The existence of divalent einsteinium is
firmly established, especially in the solid phase; such +2 state is
not observed in many other actinides, including protactinium, uranium,
neptunium, plutonium, curium and berkelium. Einsteinium(II) compounds
can be obtained, for example, by reducing einsteinium(III) with
samarium(II) chloride.
Isotopes
==========
Eighteen isotopes and four nuclear isomers are known for einsteinium,
with mass numbers 240-257. All are radioactive; the most stable one,
(252)Es, has half-life 471.7 days. The next most stable isotopes are
(254)Es (half-life 275.7 days), (255)Es (39.8 days), and (253)Es
(20.47 days). All the other isotopes have half-lives shorter than 40
hours, most shorter than 30 minutes. Of the five isomers, the most
stable is (254m)Es with a half-life of 39.3 hours.
Nuclear fission
=================
Einsteinium has a high rate of nuclear fission that results in a low
critical mass. This mass is 9.89 kilograms for a bare sphere of
(254)Es, and can be lowered to 2.9 kg by adding a 30-centimeter-thick
steel neutron reflector, or even to 2.26 kg with a 20-cm-thick
reflector made of water. However, even this small critical mass far
exceeds the total amount of einsteinium isolated so far, especially of
the rare (254)Es.
Natural occurrence
====================
Due to the short half-life of all isotopes of einsteinium, any
primordial einsteinium--that is, einsteinium that could have been
present on Earth at its formation--has long since decayed. Synthesis
of einsteinium from naturally-occurring uranium and thorium in the
Earth's crust requires multiple neutron capture, an extremely unlikely
event. Therefore, all einsteinium on Earth is produced in
laboratories, high-power nuclear reactors, or nuclear testing, and
exists only within a few years from the time of the synthesis.
The transuranic elements up to fermium, including einsteinium, should
have been present in the natural nuclear fission reactor at Oklo, but
any quantities produced then would have long since decayed away.
Synthesis and extraction
======================================================================
Einsteinium is produced in minute quantities by bombarding lighter
actinides with neutrons in dedicated high-flux nuclear reactors. The
world's major irradiation sources are the 85-megawatt High Flux
Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL),
Tennessee, U.S., and the SM-2 loop reactor at the Research Institute
of Atomic Reactors (NIIAR) in Dimitrovgrad, Russia, 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, 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 ((249)Bk) and einsteinium and picograms of fermium.
The first microscopic sample of (253)Es sample weighing about 10
nanograms was prepared in 1961 at HFIR. A special magnetic balance was
designed to estimate its weight. Larger batches were produced later
starting from several kilograms of plutonium with the einsteinium
yields (mostly (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. 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.
Laboratory synthesis
======================
Heavy neutron irradiation of plutonium results in four major isotopes
of einsteinium: (253)Es (α-emitter; half-life 20.47 days, spontaneous
fission half-life 7×10(5) years); (254m)Es (β-emitter, half-life 39.3
hours), (254)Es (α-emitter, half-life 276 days) and (255)Es
(β-emitter, half-life 39.8 days). An alternative route involves
bombardment of uranium-238 with high-intensity nitrogen or oxygen ion
beams.
(247)Es (half-life 4.55 min) was produced by irradiating (241)Am with
carbon or (238)U with nitrogen ions. The latter reaction was first
realized in 1967 in Dubna, Russia, and the involved scientists were
awarded the Lenin Komsomol Prize.
(248)Es was produced by irradiating (249)Cf with deuterium ions. It
mainly β-decays to (248)Cf with a half-life of minutes, but also
releases 6.87-MeV α-particles; the ratio of β's to α-particles is
about 400.
:
(249, 250, 251, 252)Es were obtained by bombarding (249)Bk with
α-particles. One to four neutrons are released, so four different
isotopes are formed in one reaction.
:^{249}_{97}Bk ->[+\alpha] ^{249,250,251,252}_{99}Es
(253)Es was produced by irradiating a 0.1-0.2 milligram (252)Cf target
with a thermal neutron flux of (2-5)×10(14) neutrons/(cm(2)·s) for
500-900 hours:
:^{252}_{98}Cf ->[\ce{(n,\gamma)}] ^{253}_{98}Cf
->[\beta^-][17.81 \ce{d}] ^{253}_{99}Es
In 2020, scientists at ORNL created about 200 nanograms of (254)Es;
allowing some chemical properties of the element to be studied for the
first time.
Synthesis in nuclear explosions
=================================
The analysis of the debris at the 10-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(23) neutrons/cm(2) within a
microsecond, or about 10(29) neutrons/(cm(2)·s). In comparison, the
flux of HFIR is 5 neutrons/(cm(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.
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.
Of the nine underground tests between 1962 and 1969, 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. However, the major practical problem of the entire
proposal was collecting the radioactive debris dispersed by the
powerful blast. Aircraft filters adsorbed only ~4 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 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. 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.
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.
Separation
============
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. 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, (253)Es,
decays with a half-life of only 20 days to (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.
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 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.
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.
Preparation of the metal
==========================
Einsteinium is highly reactive, so strong reducing agents are required
to obtain the pure metal from its compounds. This can be achieved by
reduction of einsteinium(III) fluoride with metallic lithium:
:EsF + 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:
:EsO + 2 La → 2 Es + LaO
Chemical compounds
======================================================================
class = wikitable
Crystal structure and lattice constants of some Es compounds
!Compound!!Color !! Symmetry!!Space group!!No!!Pearson symbol||'a'
(pm)!!'b' (pm)!!'c' (pm)
|EsO Colorless Cubic Ia 206 cI80 1076.6
|EsO Colorless Monoclinic C2/m 12 mS30 1411 359 880
|EsO Colorless Hexagonal Pm1 164 hP5 370 600
|EsF Hexagonal
|EsF Monoclinic C2/c 15 mS60
|EsCl Orange Hexagonal C6/m hP8 727 410
|EsBr Yellow Monoclinic C2/m 12 mS16 727 1259 681
|EsI Amber Hexagonal R 148 hR24 753 2084
|EsOCl Tetragonal P4/nmm 394.8 670.2
Oxides
========
Einsteinium(III) oxide (EsO) was obtained by burning einsteinium(III)
nitrate. It forms colorless cubic crystals, which were first
characterized from microgram samples sized about 30 nanometers. Two
other phases, monoclinic and hexagonal, are known for this oxide. The
formation of a certain EsO phase depends on the preparation technique
and sample history, and there is no clear phase diagram.
Interconversions between the three phases can occur spontaneously, as
a result of self-irradiation or self-heating. The hexagonal phase is
isotypic with lanthanum oxide where the Es(3+) ion is surrounded by a
6-coordinated group of O(2−) ions.
Halides
=========
Einsteinium halides are known for the oxidation states +2 and +3. The
most stable state is +3 for all halides from fluoride to iodide.
Einsteinium(III) fluoride (EsF) can be precipitated from Es(III)
chloride solutions upon reaction with fluoride ions. An alternative
preparation procedure is to exposure Es(III) oxide to chlorine
trifluoride (ClF) or F gas at a pressure of 1-2 atmospheres and
temperature 300-400°C. The EsF crystal structure is hexagonal, as in
californium(III) fluoride (CfF) where the Es(3+) ions are 8-fold
coordinated by fluorine ions in a bicapped trigonal prism arrangement.
Es(III) chloride (EsCl) can be prepared by annealing Es(III) oxide in
the atmosphere of dry hydrogen chloride vapors at about 500°C for some
20 minutes. It crystallizes upon cooling at about 425°C into an orange
solid with a hexagonal structure of UCl type, where einsteinium atoms
are 9-fold coordinated by chlorine atoms in a tricapped trigonal prism
geometry. Einsteinium(III) bromide (EsBr) is a pale-yellow solid with
a monoclinic structure of AlCl type, where the einsteinium atoms are
octahedrally coordinated by bromine (coordination number 6).
The divalent compounds of einsteinium are obtained by reducing the
trivalent halides with hydrogen:
:2 EsX + H → 2 EsX + 2 HX; X = F, Cl, Br, I
Einsteinium(II) chloride (EsCl), einsteinium(II) bromide (EsBr), and
einsteinium(II) iodide (EsI) have been produced and characterized by
optical absorption, with no structural information available yet.
Known oxyhalides of einsteinium include EsOCl, EsOBr and EsOI. These
salts are synthesized by treating a trihalide with a vapor mixture of
water and the corresponding hydrogen halide: for example, EsCl +
HO/HCl to obtain EsOCl.
Organoeinsteinium compounds
=============================
Einsteinium's high radioactivity has a potential use in radiation
therapy, and organometallic complexes have been synthesized in order
to deliver einsteinium to an appropriate organ in the body.
Experiments have been performed on injecting einsteinium citrate (as
well as fermium compounds) to dogs. Einsteinium(III) was also
incorporated into β-diketone chelate complexes, since analogous
complexes with lanthanides previously showed strongest UV-excited
luminescence among metallorganic compounds. When preparing einsteinium
complexes, the Es(3+) ions were 1000 times diluted with Gd(3+) ions.
This allowed reducing the radiation damage so that the compounds did
not disintegrate during the 20 minutes required for the measurements.
The resulting luminescence from Es(3+) was much too weak to be
detected. This was explained by the unfavorable relative energies of
the individual constituents of the compound that hindered efficient
energy transfer from the chelate matrix to Es(3+) ions. Similar
conclusion was drawn for americium, berkelium and fermium.
Luminescence of Es(3+) ions was however observed in inorganic
hydrochloric acid solutions as well as in organic solution with
di(2-ethylhexyl)orthophosphoric acid. It shows a broad peak at about
1064 nanometers (half-width about 100 nm) which can be resonantly
excited by green light (ca. 495 nm wavelength). The luminescence has a
lifetime of several microseconds and the quantum yield below 0.1%. The
relatively high, compared to lanthanides, non-radiative decay rates in
Es(3+) were associated with the stronger interaction of f-electrons
with the inner Es(3+) electrons.
Applications
======================================================================
There is almost no use for any isotope of einsteinium outside basic
scientific research aiming at production of higher transuranium
elements and superheavy elements.
In 1955, mendelevium was synthesized by irradiating a target
consisting of about 10(9) atoms of (253)Es in the 60-inch cyclotron at
Berkeley Laboratory. The resulting (253)Es(α,n)(256)Md reaction
yielded 17 atoms of the new element with the atomic number of 101.
The rare isotope (254)Es is favored for production of superheavy
elements due to its large mass, relatively long half-life of 270 days,
and availability in significant amounts of several micrograms. Hence
(254)Es was used as a target in the attempted synthesis of ununennium
(element 119) in 1985 by bombarding it with calcium-48 ions at the
superHILAC linear particle accelerator at Berkeley, California. No
atoms were identified, setting an upper limit for the cross section of
this reaction at 300 nanobarns.
:{^{254}_{99}Es} + {^{48}_{20}Ca} -> {^{302}_{119}Uue^\ast} ->
no\ atoms
(254)Es was used as the calibration marker in the chemical analysis
spectrometer ("alpha-scattering surface analyzer") of the Surveyor 5
lunar probe. The large mass of this isotope reduced the spectral
overlap between signals from the marker and the studied lighter
elements of the lunar surface.
Safety
======================================================================
Most of the available einsteinium toxicity data is from research on
animals. Upon ingestion by rats, only ~0.01% of it ends in the
bloodstream. From there, about 65% goes to the bones, where it would
remain for ~50 years if not for its radioactive decay, not to speak of
the 3-year maximum lifespan of rats, 25% to the lungs (biological
half-life ~20 years, though this is again rendered irrelevant by the
short half-life of einsteinium), 0.035% to the testicles or 0.01% to
the ovaries - where einsteinium stays indefinitely. About 10% of the
ingested amount is excreted. The distribution of einsteinium over bone
surfaces is uniform and is similar to that of plutonium.
External links
======================================================================
* [
http://www.periodicvideos.com/videos/099.htm Einsteinium] at 'The
Periodic Table of Videos' (University of Nottingham)
* [
https://books.google.com/books?id=cgqNoNWLGBMC&pg=PA311
Age-related factors in radionuclide metabolism and dosimetry:
Proceedings] - contains several health related studies of einsteinium
License
=========
All content on Gopherpedia comes from Wikipedia, and is licensed under CC-BY-SA
License URL:
http://creativecommons.org/licenses/by-sa/3.0/
Original Article:
http://en.wikipedia.org/wiki/Einsteinium
