Heavy ions chemical effects

Since the discovery of the parton substructure of nucleons and its interpretation within the constituent quark model, much effort has been spent to explain the properties of these particles and the structure of high density phases of matter is under current experimental investigation in heavy-ion collisions [17]. While the diagnostics of a phase transition in experiments with heavy-ion beams faces the problems of strong non-equilibrium and finite size, the dense matter in a compact star forms a macroscopic system in thermal and chemical equilibrium for which effects signalling a phase transition shall be most pronounced [8],... 

In addition to the fundamental scientific aspects, many studies on the chemical effects of heavy ion radiolysis have significant practical applications. These applications range from the nuclear power industry [26,27], space radiation effects [28], medical therapy [29],... 

As in the case of fast electrons, the main contribution to energy losses of heavy charged particles (ions) comes from ionization losses (see Section V), which are responsible for most of the radiation-chemical effects. Therefore, we consider here only the structure of that part of an ion s track where the ionization losses are dominating. The role of elastic interaction between ions and atoms of the medium, which becomes essential only at the end of the ion s track, is not considered in this section. 

The role of the track structure is most clearly illustrated by the example of radiolysis of liquids by heavy ions. In this case it is possible to vary broadly the geometric dimension of tracks and the concentrations of active particles in them. The dependence of track effects on the track structure has been studied in Refs. 365 and 366 The qualitative relation between the structure of a track and the features of radiation-chemical processes has been analysed.15,18... 

The process occurring here is reminiscent of the N.I.H. shift, which is well known to occur in iron hydroxylases such as cytochrome P-450 and mammalian PAH [1,167], For example, action of PAH on [4-3H]phenylalanine produces >90% [3-3H]tyrosine. Here, a presumed electrophilic iron-oxy species produces a carbonium ion intermediate from which a 1,2-shift occurs, giving a resonance stabilized cation rearomatization through loss of H+ (or 3H+) gives the observed product as a result of a heavy atom isotope effect. Thus, it appears that the N.I.H. shift mechanism for copper has been discovered for a chemical model system prior to its observation in proteins. 

Chemical matrix effects due to space-charge ion transmission loss remain a problem. Concentrations of heavy ions as low as 100 ppm can affect sensitivity and therefore produce an analysis error. Perhaps alternative designs will reduce space-charge effects, but can the space-charge effects be significantly reduced while maintaining or continuing to improve sensitivity ... 

Even if irradiation with heavy ions concerns evidendy many materials such as solids or liquids and gases, this chapter will deal with the effect of high-energy heavy particles in liquid water. Actually, chemical mechanisms in pure water have been depicted a few decades ago and this medium is undoubtedly the one in the nature, more generally in the living systems, and also in the industry to be extensively used. Therefore this chapter tries to give the new trends of the research on water radiolysis with heavy ion beams, the methods developed with their associated problems and the facilities used for these studies. 

LaVerne JA. (2004) Radiation chemical effects of heavy ions. In Mozumder A, Hatano Y. (eds.), Charged Particle and Photon Interactions with Matter. Chemical, Physicochemical, and Biological Consequences with Applications, pp. 403-429. Marcel Dekker, New York. 

Electrons tracks are less dense than the tracks of heavy charged particles and the spurs are more widely spaced (Chapter 4). The induced physical processes are comparable in many regards to the effect of exposure to heavy particles or ions. X- and gamma rays actually are indirect methods of producing fast electrons in matter. As a consequence, chemical effects can be considered very similar in nature. Some specific features may nevertheless arise from the significantly different dose rates i.e. amount of absorbed energy per unit time) as a consequence of different LET values. 

The production of H2 in the radiolysis of water has been extensively re-examined in recent years [8], Previous studies had assumed that the main mechanism for H2 production was due to radical reactions of the hydrated electron and H atoms. Selected scavenger studies have shown that the precursor to the hydrated electron is also the precursor to H2. The majority of H2 production in the track of heavy ions is due to dissociative combination reactions between the precursor to the hydrated electron and the molecular water cation. Dissociative electron attachment reactions may also play some role in y-ray and fast electron radiolysis. The radiation chemical yield, G-value, of H2 is 0.45 molecule/100 eV at about 1 microsecond in the radiolysis of water with y-rays. This value may be different in the radiolysis of adsorbed water because of its dissociation at the surface, steric effects, or transport of energy through the interface. 

Earlier, we found that heavy-atom effect can also be observed in bioluminescent systems 3,4 bioluminescence inhibition coefficients were found to decrease in the series potassium halides KC1, KBr, and KI. Two mechanisms can be responsible for the change of the intensity of bioiuminescence in the presence of heavy ions the physicochemical effect of external heavy atom mentioned above, and the biochemical effect, i.e. interactions with the enzymes resulting in changes in enzymatic activity. A series of model experiments was conducted to evaluate the contribution of the physicochemical mechanism. These involved the photoexcitation of model fluorescent compounds close to bioiuminescence emitters in chemical nature and fluorescent properties - flavin mononucleotide, firefly luciferin and coelenteramide. These results are clear evidence of the smaller contribution of the physicochemical mechanism to the decrease in the bioiuminescence intensity for the three bioluminescent systems under study.4... 

Radiation resistance of polymer materials is of critical importance when the materials are applied in radiation environments. To y rays or electron beams, the radiation resistance is well studied, especially by JAERI [113] and CERN [114]. Polymeric materials will be applied for space or a fusion reactor as constructing or insulating materials. The materials are subjects to in-conventional radiation such as protons, heavy ions, and neutrons having high LET to materials. With this fact, radiation resistance to high LET radiation would be different from that to low LET radiation. However, the underlying radiation chemical effects that cause deterioration are cross-linking and/or main chain scission, therefore microscopic and macroscopic effects have a close correlation with each other. 

Inner electron shell vacancies can be produced by electron, proton, and heavy ion bombardments. When the vacancies are filled with electrons, characteristic X-ray emissions occur. Kiss et al. > observed the K /K, X-ray intensity change due to chemical environments by bombarding various targets of titanium, chromium, and manganese with electrons. The magnitude of the chemical effect is about 6% for titanium (TiO —Ti), for measurements performed using a Si(Li) detector. 

Radiation Chemical Effects of Heavy Ions Jay A. LaVerne... 

---