Multiple-scattering Method Research Articles

Analysis of Transmitted Gamma-Rays by Multiple Scattering Method, (I)

Dose buildup factors and number spectra of γ-rays transmitted through a homogeneous finite slab have been estimated by the multiple scattering method, taking into account scattering — including back scattering — up to the fourth order. The calculations were performed for 1.0, 3.0, 6.0, 8.0 and 10.0 MeV γ-rays normally incident on lead, iron and water slabs of thicknesses from 1 to 15 mfp. The results of the above calculations are in good agreement with those from other calculations, such as by Monte Carlo and response matrix methods, especially for heavy shielding materials of practical importance and γ-rays of high incident energy. Further, a method is proposed with which the contribution to the total dose buildup factor by the γ-rays of the fifth and higher orders of scattering can be estimated approximately. With this method, good agreement was obtained with the dose buildup factor calculated by the Monte Carlo method, even for light shielding materials and γ-rays of low incident energy.

Determination of various Mo(110) and W(110) surface structures from LEED results using a multiple-scattering method

A plane wave multiple scattering method employing simplified form factors has been used to determine the surface structure of annealed (110) faces of tungsten and molybdenum from existing LEED results. Assuming the validity of the method, it is found that these faces, after being annealed under LEED conditions, are probably covered by an overgrown monolayer sited directly above, and at a distance of 2.1 Å from, the terminal layer of the bulk structure. It is shown that ion bombardment removes this overgrown layer and reveals the bulk structure of Mo(110). Adsorbed CO on bombarded Mo(110) is shown to take up the α-sites, i.e. to position itself directly above the metal atoms, and, assuming similar form factors for the atoms in the adsorbate and adsorbent, to cover 60% of the surface.

Self-consistent multiple-scattering approach to the interpretation of low-energy electron diffraction

The central problem in the theory of diffraction by crystals, as approached from the selfconsistent multiple-scattering viewpoint, is that of determining the effective wave field incident on each atom in the crystal. A derivation is given, in outline, of the effective field equations for a model crystal in which the individual atom layers are treated explicitly. It is shown that the properties of the effective field imply the existence of two specific dynamical effects in low-energy electron diffraction intensities, namely the occurrence of fractional order peaks in intensity curves and multiple scattering resonance effects. The underlying physical processes are discussed fully with reference to simplified model crystals. Experimental evidence for both types of dynamical effects is cited. Possible future applications of the multiple-scattering method to various topics in low-energy electron diffraction are described. The applications discussed are to the effects of adsorption on intensities, to thermal diffuse scattering, to Kikuchi effects and to effects of crystal size. Finally, a discussion is given of the prospect of developing the computational side of the theory to the stage at which it is possible to make realistic calculations of beam intensities.

Kinetics of hydrolysis of fluorosulfonate ion in alkaline solution

The double-ionization energies of methylamine, dimethylamine, trimethylamine, ethylamine, propylamine and butylamine were measured and calculated. Transitions to singlet states of the ions were considered in order to complement the previously obtained information on transitions to triplet states. The double-ionization energies were determined experimentally from the positions of peaks observed in double-charge-transfer spectra. Information on the electronic transitions giving rise to the peaks was obtained by comparing the measured energies with those calculated using a semi-empirical form of the multiple-scattering Xα computational method. It was shown that for some of the dications the density of states is high. An ab-initio computational method, used with the 3-21G and 6-31G∗ basis sets, predicted quite accurately the trend in the lowest double-ionization energies measured.

Methodical remarks on the determination of the distribution of transverse momentum of secondaries produced in ultra-high-energy interactions by means of the multiple-scattering method

Methodical remarks on the determination of the distribution of transverse momentum of secondaries produced in ultra-high-energy interactions by means of the multiple-scattering method

Multiple-Scattering Methods in the Theory of Solids

Multiple-Scattering Methods in the Theory of Solids