Metallic reflection

Layer Stacks and Protective Layers. The layer stack of an MO disk consists mainly of an MO layer, a dielectric antirefiection layer, and a metallic reflection layer (Fig. 14). The thickness of the antireflection layer as well as that of the MO layer have to be properly chosen to obtain a maximum magnetooptical figure-of-mefit (FOM). The FOM can be further increased by using a quadfilayer configuration with dielectric layers on both sides of the MO layer. Practical disks use the generalized configuration 50—120-nm dielectric layer, 25—90-nm MO layer, 17—70-nm dielectric layer (for quadfilayer configuration only), and 15—150-nm reflective layer. 

The corrosion behavior of tantalum is weU-documented (46). Technically, the excellent corrosion resistance of the metal reflects the chemical properties of the thermal oxide always present on the surface of the metal. This very adherent oxide layer makes tantalum one of the most corrosion-resistant metals to many chemicals at temperatures below 150°C. Tantalum is not attacked by most mineral acids, including aqua regia, perchloric acid, nitric acid, and concentrated sulfuric acid below 175°C. Tantalum is inert to most organic compounds organic acids, alcohols, ketones, esters, and phenols do not attack tantalum. 

Heat-reflecting metals (reflective). Aluminum, nickel, stainless steel. 

The idea of electronic conductivity in the crystals of this cluster is stimulated by the metallic reflectance of the crystals. A potential conductivity is expected to be anisotropic because of the anisotropic order of the clusters inside the crystal. As a consequence, the electric resistance is expected to be smaller in the direction of the tubes than in the vertical direction where there is no graphite-like bridging between the clusters. 

Another factor that affects trends in the stability constants of complexes formed by a series of metal ions is the crystal field stabilization energy. As was shown in Chapter 17, the aqua complexes for +2 ions of first-row transition metals reflect this effect by giving higher heats of hydration than would be expected on the basis of sizes and charges of the ions. Crystal field stabilization, as discussed in Section 17.4, would also lead to increased stability for complexes containing ligands other than water. It is a pervasive factor in the stability of many types of complexes. Because ligands that form tt bonds... 

Indeed, this optical density is too large to be measnred with a spectrophotometer. Moreover, the ideal metal reflectivity is 1, so that no light would be transmitted at low freqnencies. 

Metals reflect by a process known as specular reflection, with this effect being caused by the sea of delocalized electrons on the surface of the metal. If thin enough, this sea becomes more localized, thereby diminishing the extent to which specular reflection can occur. 

Lead was smelted from one of its ores (galena) since around 3500 BC, but was not common until 1,000 years later. Tin seems to originate in Persia around 1800-1600 bc, and iron in Anatolia around 1400 bc. This sequence of discovery of the metals reflects the degree of difficulty in separating the pure metal from its ore iron clings tightly to oxygen in the common mineral ore haematite (ochre), and intense heat and charcoal are needed to prise them apart. 

Since the quantity in parenthesis is very small in metals, reflectivity is almost total up to high frequencies. 

Electronic spectra Cu1—colourless Cu11—normal d-d Cu1—colourless Cu11—near normal d-d. Characteristic (I)-(II) charge transfer spectra No spectra of constituent Cu1 and Cu11 ions. Characteristic charge transfer spectra. Metallic reflectivity... 

Detection of Sulphur Dioxide.—Sulphurous anhydride, which is often added to tanning extracts, either as such or more often as sulphites, to enhance their keeping qualities, may be detected by treating 10 grams of the extract in a beaker with 20 c.c. of hydrochloric acid and 20 c.c. of water, a piece of pure zinc being added and the beaker covered with a clock-glass under which is suspended a strip of lead acetate paper if the extract contains sulphurous anhydride, the paper becomes brown or assumes a blackish tint with metallic reflection. If the paper remains white for 15 minutes, absence of sulphurous acid may be assumed. 

Optical absorption spectroscopy No intervalence transitions in visible region One mixed-valence transition in visible region absorption bands intensify at elevated pressures and low temperatures One or more mixed-valence transitions in visible region temperature lowers intensity of absorption bands, pressure intensifies Opaque metallic reflectivity in visible region... 

To summarize, the retarded interactions are important only for small wave vectors, of the order of that of the photons. For larger wave vectors the retarded interactions are uncoupled, in the sense that they do not contribute to the local field which describes the interaction between dipoles. This property allows us to understand why in global effects (cohesion energy, dispersion, etc.) retarded interactions make very small contributions, although for small K, the retarded interactions may show very strong effects (such as the quasi-metallic reflection of certain dyes,1 s or of the second singlet of the anthracene crystal). In particular, in all phenomena that involve interactions between excitons and free radiation, the retarded effects are by no means essential. 

Reflectivity spectroscopy The quasi-metallic reflection of the bulk near the 0-0 transition is sharply modulated by well-resolved signatures of the surface and of the subsurfaces. The positions, the intensity, and the shape of the signature allow one to investigate the surface-bulk interactions.121... 

Reactive electrodes refer mostly to metals from the alkaline (e.g., lithium, sodium) and the alkaline earth (e.g., calcium, magnesium) groups. These metals may react spontaneously with most of the nonaqueous polar solvents, salt anions containing elements in a high oxidation state (e.g., C104 , AsF6 , PF6 , SO CF ) and atmospheric components (02, C02, H20, N2). Note that ah the polar solvents have groups that may contain C—O, C—S, C—N, C—Cl, C—F, S—O, S—Cl, etc. These bonds can be attacked by active metals to form ionic species, and thus the electrode-solution reactions may produce reduction products that are more stable thermodynamically than the mother solution components. Consequently, active metals in nonaqueous systems are always covered by surface films [46], When introduced to the solutions, active metals are usually already covered by native films (formed by reactions with atmospheric species), and then these initial layers are substituted by surface species formed by the reduction of solution components [47], In most of these cases, the open circuit potentials of these metals reflect the potential of the M/MX/MZ+ half-cell, where MX refers to the metal salts/oxide/hydroxide/carbonates which comprise the surface films. The potential of this half-cell may be close to that of the M/Mz+ couple [48],... 

Uranyl Platinocyanide, U02.Pt(CN)4.4(or 5)H20, has been prepared 6 by double decomposition of solutions of uranyl sulphate and barium platinocyanide. The green, filtered solution, upon evaporation at room temperature in a desiccator, deposits red crystals possessing a strong green metallic reflection. 

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