Heavy ion reaction products

In 1994 and 1995 Dr. Darleane Hoffinan of LLNL in Cahfornia and others from Germany used the Separator for Heavy Ion Reaction Products (SHIP) at the GSI laboratory in Darmstadt, Germany, to produce two new isotopes of element 110. 

The identification of the first transuranium elements was by chemical means. In the early 1960s physical techniques were developed which allowed for detection of nuclei with lifetimes of less than one second at high sensitivity. A further improvement of the physical methods was obtained with the development of recoil separators and large area position sensitive detectors. As a prime example for such instruments, we will describe the velocity filter SHIP (Separator for Heavy-Ion reaction Products) and its detector system, which were developed at the UNILAC. The principle of separation and detection techniques used in the other laboratories is comparable. 

Schematic view of the veiocity fiiter Separator for Heavy Ion reaction Products (SHiP) in its present configuration with target wheei and detector array (Hofmann and Munzenberg 2000)...

A SISAK set-up used for liquid-liquid extraction of rutherfordium from heavy-ion reaction products... 

The methods used in the investigation of heavy-ion reactions are similar to those described in section 8.6. The high linear energy transfer (LET) and the relatively short range of heavy ions have to be taken into account. On-line separation of shortlived products is of special importance. 

In this case, the recoiling products of the heavy-ion reaction were transported on the moving belt to an array of energy-sensitive solid-state detectors. The half-life of Lr was too short to allow chemical separation, and Lr was the first element to be identified by purely instrumental methods. It was named in honour of Lawrence, the inventor of the cyclotron. 

The applicability of heavy-ion reactions to the production of heavy elements increased with the development of efficient heavy-ion accelerators at Berkeley, Dubna and Darmstadt. On the other hand, the importance of instrumental methods... 

Dullmann, C. E., Eichler, B., Eichler, R., Gaggeler, H. W., Jost, D. T., Piguet, D., and Ttirler, A. 2002a. IVO, a device for in situ volatilization and on-line detection of products from heavy ion reactions. Nucl Instrum Meth A 479, 631-639. 

In heavy-ion reactions, the more general term quasielastic scatteringis frequently applied to reactions at the nuclear surface. This more inclusive definition covers not only the above mechanisms, but also multiple-nucleon-traws r reactions. In these events, two or more nucleons may be transferred, producing a more diverse array of reaction products. The multiple-nucleon-transfer mechanism can produce nuclei relatively far away from the line of beta stability. Consider the example,... 

In the study of the mechanism of heavy-ion reaction resulting in transuranium products and for investigating nuclear properties of transuranium nuclei, it is of great importance to isolate and uniquely identify the products by their atomic number Z, mass number A, and production cross sections. The claim to the discovery of a new element must present a clear evidence for unequivocal identification of Z, while that of a new isotope has to be made with the determination of both Z and A. 

In light heavy-ion reactions, the cross section for the production of heavy-element reaction products depends on the probability of formation of the highly excited compound nucleus and on the probability for this nucleus to avoid the fission process as it sheds energy by predominantly emitting nucleons and photons... 

Thermal properties of several chlorinated phenols and derivatives were studied by differential thermal analysis and mass spectrometry and in bulk reactions. Conditions which might facilitate the formation of stable dioxins were emphasized. No two chlorinated phenols behaved alike. For a given compound the decomposition temperature and rate as well as the product distribution varied considerably with reaction conditions. The phenols themselves seem to pyro-lyze under equilibrium conditions slowly above 250°C. For their alkali salts the onset of decomposition is sharp and around 350°C. The reaction itself is exothermic. Preliminary results indicate that heavy ions such as cupric ion may decrease the decomposition temperature. 

Often the products of nuclear reactions have very short half-lives. This is especially true for the heaviest elements obtained by bombardment of heavy targets with heavy ions. To identify and characterize such short-lived nuclides, fast separations are required solvent extraction techniques are well suited to provide the required fast separations. For example, the SISAK method [68] has been successfully used in conjunction with in-line gas jet separators at heavy ion accelerators to identify short half-life actinide isotopes produced by collision of heavy atoms. The Sisak method involves use of centrifugal contactors, with phase residence times as low as tenths of a second, in conjunction with in-line radiometric detection equipment. 

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