No abstract available

No abstract available

No abstract available

[en] As a basis for future heavy element experiments off-line tracer studies with rhenium have been carried out to model the chemical behavior of nielsbohrium (element 107) in thermochromatographic separations with oxygen as a reactive gas. A specific version of the On-Line Gas Phase Separation Apparatus, OLGA, has been developed to perform on-line chemical separations of short-lived products from heavy ion nuclear reactions, and to enable α-spectroscopic measurements of the separated products after condensation on thin foils. (orig.)

[en] The synthesis of 103, 105 and 107 elements through heavy ion reactions is discussed in the context of the fragmentation theory by estimating the production cross sections with the help of the statistical model, including fission competition. It is shown that the most favourable target -projectile combinations predicted by theory coincide with the ones already used in the experiments for the production of transfermium elements provided that the critical angular momentum value is determined by the condition of vanishing of the fission barrier. (author)

[en] Fully relativistic Density-Functional calculations have been performed for group 7 MO₃Cl (M = Tc, Re, and element 107, Bh), for group 8 tetroxides MO₄ (M = Ru, Os, and element 108, Hs), and for various aqueous complexes of group 6 elements Mo, W, and element 106, Sg. The electronic structure analysis has shown the transactinide compounds to be very similar to those of the lighter homologs in the respective chemical groups with the covalence increasing with increasing atomic number. Results have shown BhO₃Cl to have a trend in volatility in line with that of the lighter homologs in the group. Hydrolysis of element 106 with the formation of anionic oxo-complexes has, however, a reversed trend, so that hydrolysis decreases in the order Mo > Sg > W. (orig.)

[en] Experiments on searching spontaneously fissile isotopes of the element 107 which may be formed in berkelium 249 irradiation by neon-22 accelerated ions have been carried out using the express technique of continuous thermochromatographic separation of evaporating oxygen-containing radiorhenium compound. The spontaneous fissile recording has been performed by means of quartz traok detectors put into a column. A necessary : degree of refinement (>10⁴) from actipoid element isotopes : has been achieved in the zone of expected eka-rhenium deposition. Tracks of spontaneous fission fragments have not been found in this zone. In terms of effective cross sections of the element 107 production experiment sensitivity achieves 1^-34 cm² for isotopes with half-life period falling in the range from approximately 2 up to approximately 5x10⁴ s

[en] The thermochromatographic behavior of volatile oxygen compounds of radiorhenium was studied. These were formed in the air with different partial pressure of water vapour. The procedure of continuous thermochromatographic separation of radiorhenium from the products of nuclear reactions induced by heavy ions was developed. It is shown that not more than 10^-5 portion of atoms of ytterbium which is homologous with actionoids and of the hafnium and tungsten-the homologs of elements 104 and 105 - pass onto the column thermogradient part. It is found that under these conditions rhenium forms the adsorption zone with the centre at 100+-20 deg C. The transportation time for Re atoms from the targets is estimated to be not more than 3 s, the chemical yield of rhenium is near 80%. The developed method could be used for fast selective isolation of spontaneously fissile isotopes of element 107 as ekarhenium from a mixture of atoms with Z<=107

[en] Attempts were made to identify new elements in heavy ion fusion reactions. After an effective separation by the velocity filter SHIP the ions passed a pair of thin secondary electron detectors and were finally implanted into position sensitive Si-detectors. With these techniques the odd elements 105, 107, and 109 have been investigated in the years 1981 and 1982. The even elements 106 and 108 have been studied in the year 1984, and in 1985 attempts were made to produce element 110. So far in most experiments ²⁰⁸Pb and ²⁰⁹Bi targets have been irradiated with beams of ⁵⁰Ti, ⁵⁴Cr, ⁵⁸Fe, and ⁶⁴Ni. In a recent experiment (April/May 1986), the decay of the ee nucleus ²⁶⁴108 was measured. This isotope was produced in the reaction ⁵⁸Fe+²⁰⁷Pb with a cross section of (3.2+-_2.6^6.1) pb. The nucleus ²⁶⁴108 decays by α emission with a half-life of (76+-₃₅³⁶⁵) μs. A deduced α energy is (10.8+-_-0.3^0.1) MeV. Also ²⁶⁰106 is decaying by α emission with a branching of 50%. The decay sequence ²⁶⁴108 (α)→²⁶⁰106(α)→²⁵⁶104 (sf) demonstrates that the heavier element isotopes ²⁶⁴108 and ²⁶⁰106 are more stable against fission than the lighter element isotope ²⁵⁶104. The mass excesses of ²⁶⁴108 and ²⁶⁰106 are (120.0+-0.3) MeV and (106.58+-0.10) MeV, respectively. The values are obtained by α chain summation. The investigated isotopes are situated near the center of a shell stabilized region of deformed nuclei. The fission barriers for the discovered isotopes are mainly due to shell correction energies. Values as large as 5 MeV have been deduced from the data. The liquid drop fission barriers are negligible, the stabilization of the nuclei observed is due to shell corrections. In this sense the nuclei are deformed superheavy nuclei

[en] Heavy ion nuclear reactions may enable the answers to be found to two questions. How many chemical elements are there, and what forces terminate the periodic table at its upper end. The study of exotic nuclei, with very unusual mixing ratios of protons and neutrons, at the UNILAC is discussed, also the synthesis (by fusion) of exotic nuclei and the experimental techniques needed to study them. At the UNILAC the studies are focussed on proton-rich nuclei. Most of the new isotopes discovered fall into this region. The discovery of elements 107 and 109 at the UNILAC are explained. Attempts to produce superheavy elements by several techniques are discussed and the results explained. Nuclear fusions to be attempted are also mentioned. (U.K.)