Nuclear reaction method

This is a highly specialised technique requiring the availability of a very-high-energy (MeV) ion source, but it is the most accurate in use today for 

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The nuclear reaction methods are suitable for the determination of several isotopes from to S. The most frequently used reactions are (p, ), (d,p) and (d,a) providing useful alternative methods for the determination of isotopes such as D, and compared with RBS or elastic recoil detection analysis (ERDA). Alpha induced reactions have a limited use. Some Li induced reactions have been tested and the ( B, a) reaction has been used for hydrogen determination and profiling. Cross-sections of 10 to 100 mb sr are observed for proton and deu-teron induced reactions with light isotopes such as D, li. Be and B. Detection limits of the order of 10 jjg g or even less are then possible with measuring times of the order of tens of minutes. Isotopes up to S can be determined in heavier matrices at mg g levels depending on the maximum beam current that the sample can withstand. 

The principal methods for deterrnination of the deuterium content of hydrogen and water are based upon measurements of density, mass, or infrared spectra. Other methods are based on proton magnetic resonance techniques (77,78), F nuclear magnetic resonance (79), interferometry (80), osmometry (81), nuclear reaction (82), combustion (83), and falling drop methods (84). 

Nuclear reaction analysis (NRA) is used to determine the concentration and depth distribution of light elements in the near sur ce (the first few lm) of solids. Because this method relies on nuclear reactions, it is insensitive to solid state matrix effects. Hence, it is easily made quantitative without reference to standard samples. NRA is isotope specific, making it ideal for isotopic tracer experiments. This characteristic also makes NRA less vulnerable than some other methods to interference effects that may overwhelm signals from low abundance elements. In addition, measurements are rapid and nondestructive. 

Although following similar nuclear reaction schemes, nuclear analytical methods (NAMs) comprise bulk analysing capability (neutron and photon activation analysis, NAA and PAA, respectively), as well as detection power in near-surface regions of solids (ion-beam analysis, IB A). NAMs aiming at the determination of elements are based on the interaction of nuclear particles with atomic nuclei. They are nuclide specific in most cases. As the electronic shell of the atom does not participate in the principal physical process, the chemical bonding status of the element is of no relevance. The general scheme of a nuclear interaction is ... 

In terms of atomic spectrometry, NAA is a method combining excitation by nuclear reaction with delayed de-excitation of the radioactive atoms produced by emission of ionising radiation (fi, y, X-ray). Measurement of delayed particles or radiations from the decay of a radioactive product of a neutron-induced nuclear reaction is known as simple or delayed-gamma NAA, and may be purely instrumental (INAA). The y-ray energies are characteristic of specific indicator radionuclides, and their intensities are proportional to the amounts of the various target nuclides in the sample. NAA can thus... 

The energy of the y-rays is indicative of the isotope present, and the intensity of the y-rays is a measure of the concentration of the isotope in the sample. The limitation of this method is that, in order to have a nuclear reaction, the repulsive Coulomb barrier has to be overcome. For incident particles of energy up to 3 MeV, the only accessible elements are the light elements with Z< 15 the cross-sections of the remaining elements become rapidly negligible. 

NRA is a powerful method of obtaining concentration versus depth profiles of labelled polymer chains in films up to several microns thick with a spatial resolution of down to a few nanometres. This involves the detection of gamma rays produced by irradiation by energetic ions to induce a resonant nuclear reaction at various depths in the sample. In order to avoid permanent radioactivity in the specimen, the energy of the projectile is maintained at a relatively low value. Due to the large coulomb barrier around heavy nuclei, only light nuclei may be easily identified (atomic mass < 30). 

A detailed analysis of photoisomerization of the nitrone group in the nitroxyl radical 4-phenyl-2,2,5,5-tetramethyl-3-imidazoline-3-oxide-l-oxyl, based on double electron-nuclear resonance methods, has shown that in the absence of oxygen the photochemical reaction occurs without affecting the radical center. The... 

The title Spectroscopy in Catalysis is attractively compact but not quite precise. The book also introduces microscopy, diffraction and temperature programmed reaction methods, as these are important tools in the characterization of catalysts. As to applications, I have limited myself to supported metals, oxides, sulfides and metal single crystals. Zeolites, as well as techniques such as nuclear magnetic resonance and electron spin resonance have been left out, mainly because the author has little personal experience with these subjects. Catalysis in the year 2000 would not be what it is without surface science. Hence, techniques that are applicable to study the surfaces of single crystals or metal foils used to model catalytic surfaces, have been included. 

Glascock, M.D. (1994). Nuclear reaction chemical analysis prompt and delayed measurements. In Chemical Analysis by Nuclear Methods, ed. Alfassi, Z.B., John Wiley, Chichester, pp. 75-99. 

Until it was known that the half-life of Tc is much shorter than 10 years Herr looked for technetiimi-98 in a munber of minerals from Norway and South Africa by neutron activation analysis. This most sensitive method was also used by Alperovitch et al. and Anders et al. to detect this isotope in nature. According to the nuclear reaction... 

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. 

Fluorine-18 is readily available from cyclotrons by using a wide variety of nuclear reactions. The most common methods to produce F are given in Table 4. They will not be discussed here as more elaborated details can be... 

Nohehum may he synthesized by several methods involving irradiation of isotopes of curium, plutonium, and fermium in the form of thin targets with heavy ions of boron, carbon, and oxygen using double-recod technique. The nuclear reaction in the synthesis of No-254 carried out by Ghiorso and his group is as foUows ... 

The absolute methods (meaning no independent calibration is necessary) for determining H20t include manometry (Newman et al., 1986), Karl-Fischer titration (Behrens et al., 1996), and nuclear reaction analyses (NRA). NRA is a bulk method for H20t and requires a density estimate to convert data to weight percent. Secondary ion mass spectrometry (SIMS) can measure H20t, but it requires... 

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