Range of Heavy Ions

Results of calculations based on Eq. 4.42 are given by many authors. Based on calculations described in Ref. 12, Siffert and Coche present universal graphs for several heavy ions in silicon (Figs. 4.14 and 4.15). 

The range of a heavy ion in a compound or mixture is calculated from the range in pure elements by using the equation  

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Since the radioactive half-lives of the known transuranium elements and their resistance to spontaneous fission decrease with increase in atomic number, the outlook for the synthesis of further elements might appear increasingly bleak. However, theoretical calculations of nuclear stabilities, based on the concept of closed nucleon shells (p. 13) suggest the existence of an island of stability around Z= 114 and N= 184. Attention has therefore been directed towards the synthesis of element 114 (a congenor of Pb in Group 14 and adjacent superheavy elements, by bombardment of heavy nuclides with a wide range of heavy ions, but so far without success. 

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. 

Another method, giving better results, is based on the fact that the range of heavy ions is given, over a limited energy range, by an equation of the form... 

The Met-Tech separation process is a liquid ion exchange process for the ex situ recovery, separation, and concentration of a wide range of heavy metals. The technology is commercially available and, according to the vendor, has been tested at the pilot scale. According to the vendor, future applications will be in soil remediation, acid mine drainage, and the recycling of spent nuclear waste. 

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],... 

Figure 2 Range, csda, of some heavy ions [42] and electrons [44] in water as a function of energy. The dotted lines show the range for heavy ions of equal velocity.

The next few subsections will present data for the products in the radiolysis of water with a wide variety of heavy ions. Product yields with heavy ions are rarely constant in time, but most of them vary slowly in the microsecond region. Furthermore, most chemical systems used to probe yields with heavy ions were developed for examining fast electron or y-radiolysis in the microsecond region. The following discussion on product yields can be assumed to apply to the microsecond time regime. Because a wide range of systems are used to determine product yields, consistency between the different experiments can be obtained by examination of the material balance. The net decomposition of water can be obtained by setting the number of H atoms in each product equal to the number of H atoms in the net water decomposed to form that product and similarly for O atoms [16]. 

Fig. 1.3. A schematic representation of the disorder produced in room-temperature implantations of heavy ions at energies of 10-100 keV. At low doses, the highly disordered regions around the tracks of the ions are spatially separated from each other. The volume of the disordered region is determined primarily by the stopping point of the ion and the range of the displaced lattice atoms (dashed arrows). At high doses, the disordered regions can overlap to form an amorphous layer...

Henk RP, Benton EV (1967) Charged particle tracks in polymers No.5. A computer code for the computation of heavy ion range-energy relationships in any stopping material. U S Naval Radiological Defense Laboratory TechnRep 67-122... 

Our mass spectrometric studies have shown that major ions < 500 amu are consistent in mass with polycyclic aromatic hydrocarbon (PCAH) ions. Experimental ion mobilities of a wide mass range of PCAH ions (j, ) were extrapolated to very high masses in order to estimate the mobilities of the heavy median mass ions (Figure 1). This extrapolation parallels a Langevin-type equation. 

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