Einsteinium synthesis

It is possible to prepare very heavy elements in thermonuclear explosions, owing to the very intense, although brief (order of a microsecond), neutron flux furnished by the explosion (3,13). Einsteinium and fermium were first produced in this way they were discovered in the fallout materials from the first thermonuclear explosion (the "Mike" shot) staged in the Pacific in November 1952. It is possible that elements having atomic numbers greater than 100 would have been found had the debris been examined very soon after the explosion. The preparative process involved is multiple neutron capture in the uranium in the device, which is followed by a sequence of beta decays. Eor example, the synthesis of EM in the Mike explosion was via the production of from followed by a long chain of short-Hved beta decays,... 

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. 

The complexity of the reactions involved in the bombardment of plutonium and the production of higher transuranium elements can be seen from the following scheme which indicates the method of synthesis of einsteinium and fermium ... 

The history of syntheses saw its periods of breakthroughs and slack periods. The first breakthrough period was from 1940 to 1945 when four transuranium elements were synthesized, namely, neptunium (Z = 93), plutonium (Z = 94), americium (Z = 95), and curium (Z = 96). The period till 1949 was a slack time and no new elements were discovered. In the next breakthrough period from 1949 to 1952 four more transuranium elements were added to the periodic system, namely berklium (Z = 97), californium (Z = 98), einsteinium (Z = 99), and fermium (Z = 100). In 1955, fifteen years after the synthesis of the first transuranium element, one more element, mendelevium (Z = 101), was synthesized. The next 25 years saw much less syntheses and only six new elements appeared in the periodic system. Here scientists encountered an entirely new situation and many former criteria for evaluating discoveries of elements proved inapplicable. 

It is quite possible that nature can accomplish this synthesis through alpha decay of the dihalides of einsteinium-253. A direct synthesis would allow both absorption spectrophotometric and x-ray powder diffraction analyses, the results of which would aid in the identification of Bk(ii) species in aged einsteinium dihalide samples which also contain Cf(ii) [110,236]. 

Very heavy elements have been detected under circumstances where very intense neutron fluxes were produced. Such is the case for a few microseconds after a thermonuclear explosion. Isotopes of einsteinium and fermium were first discovered in the debris of the first thermonuclear explosion detonated at Eniwetok Atoll in November 1952 [2,5]. It is possible that elements of atomic number greater than 100 might have been detected had the debris been examined immediately after the explosion. The route whereby elements of high atomic number are formed in the detonation of a thermonuclear device is again multiple neutron capture in which is a component of the device. Thus, the synthesis... 

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