Einsteinium isotopes

Abb. 13. a-Zerfallsenergicn der Einsteinium-Isotope in Abhangigkeit der Massenzahlen. X Geradzahlige Isotope o ungeradzahlige Isotope. 

Einsteinium isotopes are separated on an ion exchange column and eluted with a solution of ammonium citrate. Radioactive isotopes are identified by an activity detector. 

The original einsteinium isotope discovered in Enewetak fallout was Es with a half-life of 20 days. Eventually other einsteinium isotopes were created under controlled conditions. The longest-lived is Es, ty, = 275 days. The longest-lived isotope of fermium is Fm, ti/, = 100.5 days. Chemically speaking, einsteinium and fermium are... 

Einsteinium-99 was found in the debris from the first thermonudear explosion on November 1,1952, at Enewetok Atoll. The einsteinium isotope obtained has a half-life of 20.5 days Fermium-100 was found in the debris from the first thermonuclear explosion at Enewetok Atoll on November 1,1952. The fermium isotope obtained has a half-life of 20.1 hours Mendelevium-101 is obtained by bombardment of einsteinium with helium ions. The mendelevium isotope obtained has a half-life of 1.3 hours... 

The use of larger particles in the cyclotron, for example carbon, nitrogen or oxygen ions, enabled elements of several units of atomic number beyond uranium to be synthesised. Einsteinium and fermium were obtained by this method and separated by ion-exchange. and indeed first identified by the appearance of their concentration peaks on the elution graph at the places expected for atomic numbers 99 and 100. The concentrations available when this was done were measured not in gcm but in atoms cm. The same elements became available in greater quantity when the first hydrogen bomb was exploded, when they were found in the fission products. Element 101, mendelevium, was made by a-particle bombardment of einsteinium, and nobelium (102) by fusion of curium and the carbon-13 isotope. 

Albert Einstein) Einsteinium, the seventh transuranic element of the actinide series to be discovered, was identified by Ghiorso and co-workers at Berkeley in December 1952 in debris from the first large thermonuclear explosion, which took place in the Pacific in November, 1952. The 20-day 253Es isotope was produced. 

Fourteen isotopes of einsteinium are now recognized. 254Es has the longest half-life (275 days). 

Fourteen isotopes are now recognized. 258Md has a half-life of 2 months. This isotope has been produced by the bombardment of an isotope of einsteinium with ions of helium. Eventually enough 258Md should be made to determine its physical properties. 

Each of the elements has a number of isotopes (2,4), all radioactive and some of which can be obtained in isotopicaHy pure form. More than 200 in number and mosdy synthetic in origin, they are produced by neutron or charged-particle induced transmutations (2,4). The known radioactive isotopes are distributed among the 15 elements approximately as follows actinium and thorium, 25 each protactinium, 20 uranium, neptunium, plutonium, americium, curium, californium, einsteinium, and fermium, 15 each herkelium, mendelevium, nobehum, and lawrencium, 10 each. There is frequently a need for values to be assigned for the atomic weights of the actinide elements. Any precise experimental work would require a value for the isotope or isotopic mixture being used, but where there is a purely formal demand for atomic weights, mass numbers that are chosen on the basis of half-life and availabiUty have customarily been used. A Hst of these is provided in Table 1. 

The effects of a rather distinct deformed shell at = 152 were clearly seen as early as 1954 in the alpha-decay energies of isotopes of californium, einsteinium, and fermium. In fact, a number of authors have suggested that the entire transuranium region is stabilized by shell effects with an influence that increases markedly with atomic number. Thus the effects of shell substmcture lead to an increase in spontaneous fission half-Hves of up to about 15 orders of magnitude for the heavy transuranium elements, the heaviest of which would otherwise have half-Hves of the order of those for a compound nucleus (lO " s or less) and not of milliseconds or longer, as found experimentally. This gives hope for the synthesis and identification of several elements beyond the present heaviest (element 109) and suggest that the peninsula of nuclei with measurable half-Hves may extend up to the island of stabiHty at Z = 114 andA = 184. 

Like einsteinium, this unstable element was discovered in the fallout from the first hydrogen bomb. To date, only fragments in microgram amounts can be isolated. 258Fm ends the series of transuranium elements that can be produced in a reactor by neutron bombardment. The longest-lived isotope decays with a half-life of 100 days... 

Radioactive, short-lived element. The longest-lived isotope (256Md) has a half-life of 55 days. To date, only a few atoms have been prepared by a nuclear reaction between einsteinium and helium nuclei in a particle accelerator. 

H. G. Jackson Isotopes of Einsteinium and Fermium Produced by Neutron Irradiation of Plutonium. Report AECL-287. Phys. Rev. 102, 203 (1956). 

In der Zwischenzeit sind zahlreiche Einsteinium- und Fermiumisotope dar-gestellt worden, so daB nun die Moglich-keit besteht, die Existenz der magischen Zahl N = 152 mittels der a-Zerfalls-energien dieser Isotope nachzupriifen. 

ISOTOPES There are total of 20 isotopes of einsteinium. Einsteinium is not found in nature. All the isotopes are radioactive and are produced artificially. Their half-lives range from eight seconds to 472 days. None have exceptionally long half-lives. 

Einsteinium s most stable isotope, einsteinium-252, with a half-life of472 days, decays into berkelium-248 through alpha decay, and then into californium-252 through beta capture. It can also change into fermium-252 through beta decay. 

Mendeleviums most stable isotope is Md-258, with a half-life of 51.5 days. It decays into einsteinium-254 through alpha (helium nuclei) decay, or it may decay through the process of spontaneous fission to form other isotopes. 

Albert Ghiorso and his team of chemists that included Glenn T. Seaborg, Stanley G. Thompson, Bernard G. Harvey, and Gregory R. Ghoppin bombarded atoms of einsteinium-253 with hehum ions in the cyclotron at the University of California at Berkeley. This resulted in a few atoms of mendelevium-256, which is one of the isotopes of mendelevium plus a free neutron. 

The first isotope of this element having mass number 253 and half-life 20 days was detected in 1952 in the Pacific in debris from the first thermonuclear explosion. The isotope was an alpha emitter of 6.6 MeV energy, chemically analogous to the rare earth element holmium. Isotope 246, having a half-life 7.3 minutes, was synthesized in the Lawrence Berkeley Laboratory cyclotron in 1954. The element was named Einsteinium in honor of Albert Einstein. Only microgram amounts have been synthesized. The element has high specific alpha activities. It may be used as a tracer in chemical studies. Commercial applications are few. 

The element first was made by Ghiorso, Harvey, Choppin, Thompson, and Seaborg in 1955 in Berkeley, California. It was synthesized by bombardment of einsteinium-253 with alpha particles of 41 MeV energy in a 60-inch cyclotron. The element was named Mendelevium in honor of Russian chemist Dimitri Mendeleev. Mendelevium —258 isotope with a half-life of 60 days was discovered in 1967. The element has no commercial use except in research to synthesize isotopes of other transuranium elements. 

All isotopes of medelevium have been synthesized by other nuclear reactions since its discovery. They are prepared by bombarding uranium, einsteinium, and californium isotopes with heavy ions, such as boron-11, carbon-12 and carbon-13. 

EINSTENIUM. CAS 7429-92-71. Chemical element symbol Es, at. no. 99. at. wt. 254 (mass number of the most stable isotope), radioactive metal of the Actinide series, also one of the Transuranium elements. Both einsteinium and fermium were formed tit a thermonuclear explosion that occurred in the South Pacific in 1952. The elements were identified by scientists from the University of California s Radiation Laboratory- the Argonnc National Laboratory, and the I. os Alamos Scientific Laboratory. It was observed that very heavy uranium isotopes which resulted from the action of the instantaneous neutron dux on uranium (contained in the explosive device) decayed to form Es and Fm. The probable electronic configuration of Es is... 

All known isotopes of einsteinium are radioactive. The first evidence of lltcir existence was obtained by ion-exchange methods applied lo coral rocks obtained from Eniwetok Atoll alter (he thermonuclear explosion. The first pure isotope found was 3,3Es produced by prolonged treatment of plutonium-239 with neutrons in the Area. Idaho. Testing Reactur. The most stable is JMEs. half-life 270 days, and therefore the mass number 254 is carried in the atomic weight tabic. Others include - Es- Es. 48Es- Es, and s Es. Es. 

The discovery of fermium (also einsteinium) was not the result of very carefully planned experiments, as in the cases of the other trans uranium elements, bill fermiuni and einsteinium were found in Ihe debris of an atomic weapon lest in the Pacific in November 1952. Researchers, using the Oak Ridge High Flux Isotope Reactor (HFIR) which produced 3.2-hour " Fm. determined ihe magnetic moment of the atomic ground state of the neutral fermium atom with a modified atomic beam magnetic resonance... 

The nuclear area is one that has been heavily dependent upon isotope ratio mass spectrometry performed by thermal ionization. Applications in this area are among the major reasons for the continued push to analyze smaller and smaller samples. There are two primary reasons for this (1) maximum practicable reduction of the hazards associated with radioactivity and (2) presence of often only a very small amount of the target element available. Areas addressed include evaluation of uranium enrichment processes [86], isotopic analysis of transuranium elements (all elements through einsteinium have been analyzed) [87], and environmental monitoring for release of uranium and other actinides [88,89]. This last area has received renewed emphasis in the wake of the Gulf War [90]. 

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