Diffusivity radiation damage

The idea of point defects in crystals goes back to Frenkel, who in 1926 proposed the existence of point defects to explain the observed values of ionic conductivity in crystalline solids. In a crystal of composition MX such as a monovalent metal halide or a divalent metal oxide or sulfide, volume ionic conductivity occurs by motion of positive or negative ions in the lattice under the influence of an electric field. If the crystal were perfect, imperfections, such as vacant lattice sites or interstitial atoms, would need to be created for ionic conductivity to occur. A great deal of energy is required to dislodge an ion from its normal lattice position and thus the current in perfect crystals would be very, very small under normal voltages. To get around this difficulty, Frenkel proposed that point defects existed in the lattice prior to the application of the electric field. This, of course, has been substantiated by subsequent work and the concept of point defects in all classes of solids, metals, ionic crystals, covalent crystals, semiconductors, etc., is an important part of the physics and chemistry of crystalline solids, not only with respect to ionic conductivity but also with respect to diffusion, radiation damage, creep, and many other properties. 

There are two other methods in which computers can be used to give information about defects in solids, often setting out from atomistic simulations or quantum mechanical foundations. Statistical methods, which can be applied to the generation of random walks, of relevance to diffusion of defects in solids or over surfaces, are well suited to a small computer. Similarly, the generation of patterns, such as the aggregation of atoms by diffusion, or superlattice arrays of defects, or defects formed by radiation damage, can be depicted visually, which leads to a better understanding of atomic processes. 

In standard FAB, the surface of the matrix solution is depleted of analyte and suffers from radiational damage during elongated measurements. Refreshment of the surface proceeds by diffusion (limited by the viscosity of the matrix) or evaporation. Continuous-flow fast atom bombardment (CF-FAB) continuously refreshes the surface exposed to the atom beam. [107,108] The same effect is obtained in slightly different way by the frit-fast atom bombardment (frit-FAB) technique. [109,110] In addition, both CF-FAB and frit-FAB can be used for online-coupling of liquid chromatography (LC, Chap. 12) [111] or capillary electrophoresis (CE) to a FAB ion source. [112]... 

Diffraction properties of crystals are determined by X-ray analysis which is covered in Chapters 4 and 5. Imperfections within the crystal are indicated by high mosaicity exhibited by broadening of diffraction spots and diffuse scattering. Prolonged exposure of protein and protein-DNA crystals to X-rays causes loss of diffraction due to radiation damage. 

Radiation damage may cause at least two effects on diffusion. One is that radiation damage results in defects in crystalline structures, and they facilitate diffu-... 

Shuster DL, Rowers RM, Farley KA (2006) The influence of natural radiation damage on helium diffusion kinetics in apatite. Earth Planet Sci Lett 249 148-161... 

Reflectance spectra are usually measured using a diffuse reflectance accessory with an integrating sphere attached to a spectrophotometer. Spectra are referenced against a reflectance standard, such as smoked MgO, barite or Halon powder. The latter is a commercial fluorocarbon that does not absorb water or suffer radiation damage as does MgO. Each of these standards is virtually free of spectral features in the wavelength range 0.3 to 2.5 pm. 

Waite, T. R. Theoretical Treatment of the Kinetics of Diffusion-Limited Reactions. Phys. Rev. 107, 463 (1957) Diffusion-Limited Annealing of Radiation Damage in Radium. Phys. Rev. 107, 471 (1957). 

---