17 research outputs found
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Measurement of the 208Pb(55Mn,n)262Bh excitation function
The excitation function for the 208Pb(55Mn,n)262Bh reaction has been measured for the first time. Using the Berkeley Gas-filled Separator at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron, a total of 33 decay chains attributable to 262Bh were observed at three different projectile energies. The existence of a previously reported alpha-decaying isomeric state was confirmed, although the production of the ground state was favored at all three energies. Additionally, 2 decay chains attributable to 261Bh were observed. The observed cross sections are much larger than those reported for the analogous 209Bi(54Cr, n)262Bh reaction, suggesting that in the latter case the projectile energies used were too high for optimum production of the 1n product. These results will be compared with predictions for the location of the excitation function maximum and the maximum cross section using the "Fusion by Diffusion" theory proposed by Swiatecki, Siwek-Wilczynska, and Wilczynski
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Development of an odd-Z-projectile reaction for heavy element synthesis: 208Pb(64Ni, n)271Ds and 208Pb(65Cu, n)272111
Seven {sup 271}Ds decay chains were identified in the bombardment of {sup 208}Pb targets with 311.5- and 314.3-MeV {sup 64}Ni projectiles using the Berkeley Gas-filled Separator. These data, combined with previous results, provide an excitation function for this reaction. From these results, an optimum energy of 321 MeV was estimated for the production of {sup 272}111 in the reaction {sup 208}Pb({sup 65}Cu, n). One decay chain was observed, resulting in a cross section of 1.7{sub -1.4}{sup +3.9} pb. This experiment confirms the discovery of element 111 by the Darmstadt group who used the {sup 209}Bi({sup 64}Ni, n){sup 272}111 reaction
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Use of the Berkeley gas-filled separator to study cold fusion reactions leading to the production of elements 110, 111, and 107
The production of neutron-deficient transactinide isotopes using cold fusion reactions has been studied in recent experiments with the Berkeley Gas-filled Separator (BGS). These experiments were part of a systematic study of using odd-Z projectile reactions for heavy element synthesis. Targets of 208Pb were bombarded with projectiles of 64Ni, 65Cu, and 55Mn to produce 271Ds, 272-111, and isomers of 262Bh, respectively. The excitation function of the 208Pb(64Ni,n)271Ds reaction was measured and seven atoms of 271Ds were produced. This result was used to estimate the optimum beam energy for the 208Pb(65Cu,n) reaction, and one decay chain of 272-111 was observed. Lastly, the excitation function of the 208Pb(55Mn,n)262Bh reaction was measured and preliminary results will be presented. These results will be characterized in terms of the performance and use of the BGS for heavy element production
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Zirconium and hafnium extraction using crown ethers - a model system for the study of rutherfordium
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Attempt to confirm superheavy element production in the 48Ca + 238U reaction
An attempt to confirm production of superheavy elements in the reaction of 48Ca beams with actinide targets has been performed using the 238U(48Ca,3n)283112 reaction. Two 48Ca projectile energies were used, that spanned the energy range where the largest cross sections have been reported for this reaction. No spontaneous fission events were observed. No alpha decay chains consistent with either reported or theoretically predicted element 112 decay properties were observed. The cross section limits reached are significantly smaller than the recently reported cross sections