Heavy-ion induced reactions

The study of heavy-ion-induced reactions is a forefront area of nuclear research. By using heavy-ion-induced reactions to make unusual nuclear species, one can explore various aspects of nuclear structure and dynamics at its limits. Another major thrust is to study the dynamics and thermodynamics of the colliding nuclei. 

Production of the elements in heavy ion-induced reactions with radioactive targets... 

A typical fission fragment angular distribution for a heavy-ion-induced fission reaction is shown in Figure 11.21. As one can see, the fragments are emitted... 

One of the early hopes of heavy ion induced transfer reactions was that new states in nuclei would be preferentially populated The fact that this hope diminished was due primarily to insufficient understanding of the reaction mechanism, but also to the generally poorer energy resolution obtained with heavy ions as compared to light ions. In this paper, I hope to demonstrate that with the proper kinematical conditions there is a remarkable selectivity which can be. obtained with a proper. choice of the reaction and that these reactions can be valuable spectroscopic tools The data in this talk have been taken using beams from the Brookhaven National Laboratory double MP tandem facility with particles identified in the focal plane of a QDDD spectrometer ... 

In summary, the selectivity of certain heavy ion reactions have been used to identify two proton and two neutron states of high spin (both yrast and non-yrast) in Nd nuclei The first direct information about the configurations of some of these states has been obtained and the results suggest simple configurations for some but not all of them At the same time certain members of the neutron 7/2 13/2 multiplet are not seen and comprehensive shell model calculations would be very useful to determine the reason Heavy ion induced transfer reactions, if chosen carefully are valuable spectroscopic tools,... 

Distribution of partial cross sections tri as a function of angular momentum quantum number i, decomposed according to reaction mechanism. Left panel is for light-ion-induced reactions (H, He) and right panel for heavy-ion reactions... 

Neutron-rich nuclides are inaccessible via the compound nuclear reaction. To produce neutron-rich transuranium nuclides, heavy-ion-induced transfer reactions of actinide targets ranging from to Es with a variety of incident particles ranging from to have been studied. 

The heavy isotopes or francium can be formed by irradiation of uranium or thorium by protons of high energy the lighter isotopes can be obtained by nuclear reactions induced in gold, tellurium, or lead targets by heavy ions. 

Reactions of atomic carbon, produced by nuclear reactions, with a number of hydrocarbons have been studied by Wolfgang and his collaborators (69). To minimize radiation induced secondary reactions which occur when use is made of C14, a technique has been developed using short-lived C11 produced by a neutron exchange reaction between a platinum foil and a C12 ion beam from a heavy ion accelerator. Part of the scattered Cu atoms has been allowed to penetrate through the thin brass foil wall of a brass vessel and come in contact with the compound wrhose reaction is studied. Products have been analyzed by gas chromatography using a technique of simultaneous mass and radioactivity determination. 

The various types of accelerators offer the possibility of applying a great variety of projectiles of different energies. The most frequently used projectiles are protons, deuterons and a particles. Some features of the reactions induced by these partieles are summarized in Table 12.4. Neutrons may be produced indirectly by nuclear reactions, y rays are generated as bremsstrahlung in electron accelerators, and heavy ions are available in heavy-ion accelerators. 

The concern of cosmochemistry is the investigation of extraterrestrial matter (sun, moon, planets, stars and interstellar matter) and their chemical changes. Meteorites are an object of special interest in cosmochemistry, because of the nuclear reactions induced by high-energy protons in cosmic radiation ( (p) up to about 10 GeV) and by other particles, such as a particles and various heavy ions. Measurement of the radionuclides produced in meteorites by cosmic radiation gives information about the intensity of this radiation in interstellar space and about the age and the history of meteorites. 

As no large difference of G(H2) between low LET and ion beam radiolysis was observed [12], as mentioned before, much interest has been paid to aromatic hydrocarbons. In 1990s, precise analysis was reported on the radiolytic products induced by irradiation of cyclopentane [73], cyclohexane [74] and cyclooctane [75] with low LET and heavy ion beams ( H, He, C and 0). The combination of gas chromatography and mass spectroscopic analysis enabled to detect the pM level products after the irradiation with 250Gy to avoid the secondary reaction of the products. Scavenging methods by using I2 as a radical scavenger were also used. Before the introduction of the results, the basic idea will be briefly presented. 

Silver also has been demonstrated to be reactive in solution systems. Thus, silver perchlorate has been shown to influence the photochemical reactivity of stilbene in acetonitrile and methanol. The fluorescence of the stilbene is quenched on addition of the perchlorate and this is good evidence for the enhancement of the So-Ti crossing induced by the heavy ion Ag+. It seems likely that an Ag+/stilbene complex is formed. The perturbation of the system is better in methanol than in acetonitrile. However, cis.trans isomerism of the stilbene is reduced within the excited Ag+/stilbene complex since it is difficult for the geometrical isomerism to occur. Enhanced isomerism is observed with the Ag+/azobenzene system. In this complex there are steiic problems encountered in the nitrogen rehybridization process that is operative in the isomerism . Enhanced So-T crossing is also seen in the Ag+/1 1 complex with tryptophan where the fluorescence is quenched and there is a threefold increase in phosphorescence . Complexes between Ag+ and polynucleotides and DNA cause quenching of the fluorescence. Enhancement of phosphorescence and a 20-fold increase in the dimerization of thymine moieties has also been observed when silver ions are added to the reaction system . ... 

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