Irradiation with X-Rays

X-rays, very common in medicine and in materials characterization, are not so frequently used for production or improvement of properties of materials and composites as the y-rays or e-beam, described earlier. The products are elemental metals in the form of nanostructures, several oxides, and salts. Thus, reductant, stabilizer-free colloidal gold solutions were fabricated by a new room-temperature synchrotron x-ray irradiation method (Yang et al 2006 Wang et al., 2007). 

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X-ray spectroscopy Analytical method by which a sample is irradiated with X-rays, characteristic radiation being emitted after scattering from the specimen. The detection limits for various elements are of the ordering cm. ... 

Once mounted in the diffractometer, the crystal is irradiated with X rays, usually so-called Cu/Cg radiation with a wavelength of 0.154 nm. When the X rays strike the enzyme crystal, they interact with electrons in the molecule and are scattered into a diffraction pattern, which, when delected and visualized, appears as a scries of intense spots against a null background. 

What is the nature of the defects seen in the EPR spectra For alkali and alkali earth halogenides it is well known that irradiation with X-ray, neutrons, gamma-radiation, or electrons produce paramagnetic color centers (F-center) [109-111]. If these centers are created in large amounts, they can be stabilized by the formation of metal clusters as observed for MgCl2 films after prolonged electron radiation [106]. From the temperature dependence... 

In the course of studies on other pathological amino acidurias, the accompanying peptiduria has also been observed by many authors. Rapp de Eston et al. (R2) observed a marked increase in the excretion of both free amino acids and peptides in patients with diffuse hepatic necrosis. Using a simplified chromatographic method adapted to clinical purposes and suitable for analysis of amino acids excreted with urine, Skarzynski et al. (S5) demonstrated a raised level of a certain peptide which is always present in normal urine in smaller quantities, as well as the appearance of some new peptides in cases of jaundice and liver cirrhosis. Some abnormal peptide spots were also detected on the chromatograms in cases of progressive muscular dystrophy (K4) and in patients irradiated with X-rays (S2). 

Figure 4 (a) Lethal effect and (b) induction of genetic changes in yeast cells irradiated with x-rays tuned to resonance absorption peak [2.153 keV (triangle)] and both sides of the peak [2.147 eV (square) and 2.160 keV (circle)]. (From Ref. 18.)... 

The anion Cl has been reported in potassium chloride crystals irradiated with x-rays at the temperature of liquid nitrogen.51 It may... 

The BaFBr Eu2 + phosphors are gaining increasing industrial importance because of their storage effect. On irradiation with X rays (or UV light) some of the Eu2 + ions are ionized to Eu3+ with loss of electrons to the conduction band. These electrons are captured by F+ centers (anion vacancies) and can be liberated from these traps by the action of light (stimulation). The electrons return to the Eu3 + ions via the conduction band, converting them to Eu2+ [5.413]-[5.417],... 

When AX (e.g., KC1) is irradiated with X-rays (or electrons), pairs of anionic Frenkel defects (Le., Xf, V ) are formed. Most of them recombine, but a small fraction separates and becomes so-called H(X ) and F(Vx) centers. Depending on the tempera-... 

COLOR CENTERS. Certain crystals, such as the alkali halides, can be colored by the introduction of excess alkali metal into the lattice, or by irradiation with x-rays, energetic electrons, etc. Thus sodium chloride acquires a yellow color and potassium chloride a blue-violet color. The absorption spectra of such crystals have definite absorption bands throughout the ultraviolet, visible and near-infrared regions. The term color center is applied to special electronic configurations in the solid. The simplest and best understood of these color centers is the F center. Color centers are basically lattice defects that absorb light. 

Exercise 29-7 When polyethene (and other polymers) are irradiated with x rays, cross-links are formed between the chains. What changes in physical properties would you expect to accompany such cross-linking Would the polyethene become more flexible Explain. 

Exercise 29-9 The material popularly known as Silly Putty" is a polymer having an —O—Si(R)2—O—Si(R)2—O— backbone. It is elastic in that it bounces and snaps back when given a quick jerk, but it rapidly loses any shape it is given when allowed to stand. Which of the polymers listed in Table 29-1 is likely to be the best candidate to have anything like similar properties Explain, What changes would you expect to take place in the properties of Silly Putty as a function of time if it were irradiated with x rays (see Exercise 29-7) ... 

Zakharov et al (Ref 188) reported on the effect of prior irradiation with X-rays, protons and neutrons on the thermal decompn of AP. 

The most recent and most puzzling example of anionic initiation is that which seems to take place when monomer is subjected to ionizing radiation at low temperatures. Acrylonitrile polymerizes rapidly at temperatures well below 0° (and even in the solid at —196°) when irradiated with X-rays or with electrons. Since it is now known that cationic polymerization may be induced by radiation, there has been speculation that similar anionic polymerization might be occurring with acrylonitrile (87, 121). This subject has been discussed recently by Magat (95) who quotes unpublished work of Bensasson and of Tabata and Hiroshi. 

X-ray photoelectron spectroscopy measures the energy distribution of the core electrons emitted from a compound on irradiation with X rays.68 69 The electron... 

In 1927, Muller had discovered that irradiation with X-rays caused mutations to appear in Drosophila at a higher rate than they did spontaneously and so X-rays became a tool for advancing the genetic studies of this organism (Muller, 1927). L.J. Stadler independently discovered the same phenomenon in barley, but published a year later (Stadler, 1928). These observations also provided the link between the inter-twined histories of research into DNA repair and cancer. To quote Muller ... 

As the name XPS implies, the analytical sample is irradiated with x-ray light and the energy distribution of the emitted photoelectrons is recorded. Fig. 1 shows a comparison between the four different processes which are caused by the interaction between x-ray photons and matter, and which can be observed by four different spectroscopic techniques 17,I8). 

Air (total chromium) Air particulate matter collected on filter is cut out and irradiated with X-ray photons XRF 0.017 pg/m3 No data Wiersema et al. 1984... 

Investigation of tumour frequencies in animals after incorporation of Sr or Ra, or irradiation with X rays or electrons, indicates a threshold dose of <5 Gy, below which no effects are observed. The effects of large single doses on man are summarized in Table 22.7. 

In 1961 Hayes and Twidell (8) found that if calcium fluoride crystals containing trivalent thulium were irradiated with x-rays, some of the thulium was converted to the divalent state. This discovery was the first of many in the study of dilute solutions of divalent rare earth ions. Most workers prefer to study the alkaline earth fluorides since these materials are stable with respect to air and have more attractive mechanical properties than the alkaline earth chlorides, bromides, and iodides. Enough work has been carried out in these softer materials to show that reactions similar to those in the fluorides do occur. 

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