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991.
The emission of molecules during bombardment of several alkali halides with a 540 eV electron beam has been investigated. Using a time of flight method the energy distributions of the halogen molecules have been measured at various temperatures of the target. The relative halogen molecule to atom ratio has also been examined as a function of the target temperature. It has been found that the molecules were formed from the atoms at the alkali halide surface. This process and the subsequent desorption of the molecules account for the experimental results. 相似文献
992.
The position of adsorbed oxygen on Cu(10) surfaces was determined with Low Energy Ion Scattering (LEIS). The experiments were performed by bombarding the copper surface at small angles of incidence with low energy Ne+ ions (3–5 keV). Measurements of the Ne+ ions scattered by adsorbed oxygen showed regular peaks in the azimuthal distribution of the scattered ions due to a shadowing effect. From the symmetry of the azimuthal distributions it follows that the centre of an adsorbed oxygen atom on the Cu(1̄10) surface lies about 0.6 Å below the midpoint between two neighbouring Cu atoms in a 〈001〉 row. A comparison of the azimuthal distributions of Ne+ ions scattered from clean Cu surfaces and oxygen-covered Cu surfaces showed that hardly any surface reconstruction had occurred in the oxygen-covered surfaces. The applied method seems to be an appropriate one for locating adsorbed atoms because it uses only simple qualitative considerations about azimuthal distributions of scattered ions. 相似文献
993.
H. A. P. De Jongh C. R. H. I. De Jonge H. J. M. Sinnige E. P. Magr W. J. Mijs 《Journal of polymer science. Part A, Polymer chemistry》1973,11(2):345-352
Bifunctional arylcyanoacetic esters were oxidatively coupled to high molecular weight, colorless, amorphous polymers, soluble in common organic solvents. Brittle films were obtained by casting or compression molding. Thermal stability of the polymers is poor due to the weak C? C bond formed by oxidative coupling. Radical dissociation-recombination of this bond (evidenced by ESR) results in meso-dl equilibration, lowering the Tg of the polymers. 相似文献
994.
We discuss some features of one dimensional superflow in a p-state superfluid. The direction l of the orbital momentum is anchored at the walls, but l tends to become aligned along the flow lines, when the superfluid velocity exceeds a certain threshold. 相似文献
995.
Magnetic properties of nickel catalysts vary by gas adsorption. In this paper, the variation of magnetic susceptibility and of saturation magnetization with chemisorption are derived taking into account the possibility of preferencial fixation on ferromagnetic particles of given size: high field techniques enable one to calculate a parameter α, the overal magnetic moment change in the fixation of one molecule; if the sample is superparamagnetic, low field techniques give (1 + A) α, where A depends upon the particle size distribution and upon a function which describes the preferencial adsorption. Experimental results concerning adsorption of O2 and H2 on NiSiO2 catalysts are reported; they are interpreted by assuming that H2 is uniformly adsorbed on the metal surface and that O2 is preferencially fixed on small particles. Some comments are added about the adsorption of hydrocarbons on nickel. 相似文献
996.
G. Cimino S. De Stefano L. Minale R. Riccio K. Hirtosu J. Clardy 《Tetrahedron letters》1979,20(38):3619-3622
The structures of two unique sesterpenes, toxislylide A and B, have been deduced by chemical, spectral, and x-ray crystallographic studies. They are components of the sponge . 相似文献
997.
Marten De Boer 《General Relativity and Gravitation》1981,13(9):837-852
A class of exact solutions-depending upon two dimensionless parameters-to the gravitational field equations is obtained, where the source of the field is a rotating, hollow cylinder of infinite length. The material properties, although highly idealised, nevertheless are not unrealistic and chosen in such a way as to allow elementary integration. The solutions show how the inertial frame inside the cylinder is dragged by the rotating material, and also how the drag continues inside the material and in the outside region. They are exact examples for the Lense-Thirring effect. 相似文献
998.
When Langmuir-Blodgett films, consisting of a mixture of a long chain carboxylic acid and its salt are immersed in benzene, the acid dissolves, while the salt remains as a skeleton. The density of the film is lowered in this way and so is the refractive index. The process can thus be followed by performing ellipsometric measurements as a function of time of skeletonization. It is established that skeletonization is, in first instance, a diffusion-controlled process with a diffusion coefficient of about at room temperature. The salt also slowly dissolves at a rate of about . 相似文献
999.
R. De Meersman 《Journal of Computational and Applied Mathematics》1976,2(1):63-65
Based on an orthogonalization technique, published earlier in this journal, a derivation is given of the Levinson algorithm for solving systems with a symmetric positive definite Toeplitz matrix. 相似文献
1000.