Single-crystal X-ray diffraction at megabar pressures and temperatures of thousands of degrees

The most reliable information about crystal structures and their response to changes in pressure and temperature is obtained from single-crystal diffraction experiments. We have developed a methodology to perform single-crystal X-ray diffraction experiments in laser-heated diamond anvil cells and demonstrate that structural refinements and accurate measurements of the thermal equation of state of metals, oxides and silicates from single-crystal intensity data are possible in pressures ranging up to megabars and temperatures of thousands of degrees. A new methodology was applied to solve the in situ high pressure, high temperature structure of iron oxide and study structural variations of iron and aluminum bearing silicate perovskite at conditions of the Earth's lower mantle.     

Two-dimensional autocorrelation function analysis of smoked foil patterns

Digital image processing techniques have been applied to the analysis of cellular smoked foil patterns from gaseous detonations. In particular, the two-dimensional autocorrelation function is applied to digital cell pattern images and an orientational correlation parameter is calculated. Taking line profiles along the directions of highest correlation provides an unbiased method of determining the mean cell size in each of the two principal directions. By analyzing the width, amplitude and angular position of the orientational correlation plots, information can be extracted concerning the cellular pattern regularity, the relative angular correlation between two sets of transverse waves in two directions, and the mean shape or elongation of the cells within the pattern. The technique is applied to smoked foils from oxyacetylene mixtures with argon dilutions ranging from 0 to 75% to quantify the increase in regularity with argon dilution. This method provides a simple and useful way of analyzing cellular patterns and constitutes a promising technique for improving smoked foil diagnostics.     

Nanostructure fabrication by glancing angle ion beam assisted deposition of silicon

Glancing angle deposition by utilizing an ion beam sputter process and a controlled substrate rotation is used to deposit silicon nanostructures with different structure varieties. The structures are grown on seeded and plain [100] silicon substrates at room temperature. The ratio of deposition rate to substrate angular frequency and the substrate surface properties determine the nanostructure geometry, size and assembly. PACS 61.46.+w; 81.05.Gc; 81.15.Cd     

Matrix relativistic wave equations

The matrix notation of paper I is extended to include first-rank spinors expressed as two-component spin-vectors. Well-known two-component and four-component spinor equations are expressed in this notation. In addition, it is shown how other covariant wave equations can easily be invented. A certain nonlinear equation is found to have only positive-energy solutions for particles and antiparticles.     

A study of the reactions γp→ωp and γp→ωp and γp→ωΔ+

The differential and total corss sections and the decay density matrix elements have been measured for the reactions, γp→ωp and γp→ωΔ⁺ (1232) in the photon energy range 2.8 to 4.8 GeV. The total cross sections for ωΔ⁺ (1232) photo-production are found to be slightly larger than those for elastic ω photo-production in this energy range. The data are compared to the predictions of a theoretical model and the contributing exchange mechanics are discussed.     

X-ray photoelectron spectroscopy of nitroanilines and their derivatives

N 1s core-electron spectra have been studied for nitroanilines and related compounds. The spectral data are qualitatively interpreted by means of the molecules-in-molecule method, which describes the interaction between the aromatic amine part (donor moiety) and the nitro group (acceptor moiety) in terms of a composite system consisting of a donor and an acceptor. It was found that the nitro-N 1s spectra and the separation between the nitro-N 1s and the amino-N 1s ionization energies depend upon the magnitude of the intramolecular charge-transfer interaction in the ground state. A similarity between the relaxation effect in the nitro-N 1s or nitro-O 1s core-hole ion and a nitration reaction of the donor moiety is demonstrated.     

Assignment of the doublet states arising from ionization of chlorine lone-pairs in molecules possessing C2υ symmetry

The He(I) photoelectron spectra of Cl₂CCH₂, Cl₂CCF₂, Cl₂CF₂ and Cl₂CBr₂ have been recorded. Detailed assignments of the