Reflection non-specular

Non-specular reflection is another term for diffuse reflection. Also the German term Remission may be used to denote the English term diffuse reflection. This is the fraction on the total incident light that is reflected and varies with the wavelength distribution of the incident light. 

Of the many X-ray based techniques available, a very powerful approach for probing interfacial structures is based on the measurement of X-ray reflectivity. The X-ray reflectivity is simply defined as the ratio of the reflected and incident X-ray fluxes. In the simple case of the mirror-like reflection of X-rays from a surface or interface, i.e., specular reflectivity, the structure is measured along the surface normal direction. Lateral structures are probed by non-specular reflectivity. The measurement and interpretation of X-ray reflectivity data (i.e., the angular distribution of X-rays scattered elastically from a surface or interface) (Als-Nielsen 1987 Feidenhans l 1989 Robinson 1991 Robinson and Tweet 1992) are derived from the same theoretical foundation as X-ray crystallography, a technique used widely to study the structure of bulk (three-dimensional or 3D) materials (Warren 1990 Als-Nielsen and McMorrow 2001). The immense power of the crystallographic techniques developed over the past century can therefore be applied to determine nearly all aspects of interfacial structure. An important characteristic of X-ray reflectivity data is that they are not only sensitive to, but also specifically derived from interfacial structures. 

Active area corrections (non-specular reflectivity). The active area correction for non-specular reflectivity becomes more complicated because it relies on determining the overlap of the incident and detector footprints, which might not have a simple analytical form. In Figures 11B-D, we show representative examples. For a four-circle spectrometer in the symmetric scattering mode (i.e., a, = af), with an incident beam shape of At = 0.5 mm by Av= 0.1 mm and a square 10 mm by 10 mm sample, we show the incident and detector footprints at selected values of Qz for a non-specular CTR with Qn =1.2 A-1 and Qz varying from 1.8 A-1 to 7.2 A-1. This calculation shows that the beam footprint becomes highly skewed as Qz increases at constant Qn, and the overlap of the incident... 

Figure 11. (A) A typical scattering geometry for specular reflectivity, showing that the active area is determined by the incident beam cross section and the incident angle, a,. (B-D) An image of the active area for non-specular reflectivity measurements, with the overlap of the incident and detector footprints shown in three regimes at Q- values of (B)1.8 A-1, (C) 3.6 A 1, and (D) 7.2 A"1, each calculated for Q = 1.2 A"1. In each case the large square indicates the 10 mm by 10 mm sample boundaries, and the sample is viewed from above the surface plane. (B) and (D) show regimes where the reflectivity can be measured with minimal systematic error because the active area will be insensitive to imperfections in the lineup that may shift the positions of the incident beam and detector footprints from their expected locations.

Non-specular reflectivity measurements have been done in a few cases to probe mineral-fluid interface structure (Geissbuhler 2000 Eng et al. 2000 Trainor et al. 2002), but their application has been limited. The use of non-specular measurements directly reveals the lateral structure of these interfaces which, in many cases, is critical for distinguishing between different structural models and uniquely identifying the lateral adsorption geometry for an adsorbate. Such measurements reveal much greater detail of... 

An important practical feature of experimental reflectivity data is that contributions to the measured reflectivity can arise trom background signal. Background can arise fi-om several sources examples are non-specular reflection from a rough surface, small-angle scattering ft om the bulk sample and... 

Non-specular reflectance Reflectance other than the mirror reflectance that occurs at the angle equal and opposite to the incident angle diffused reflectance. 

As well as influencing the rate of metal removal, the electrolytes also affect the quality of surface finish obtained in ECM, although other process conditions also have an effect. Depending on the metal being machined, some electrolytes leave an etched finish, caused by the non-specular reflection of light from crystal faces electrochemically dissolved at different rates. Sodium chloride electrolyte tends to produce an etched, matte finish with steels and nickel alloys a typical surface roughness would be about 1 pm Ra,... 

In order to study the identity and nature of the intermediate, Aylmer-K.elly et al. (1973) employed modulated specular reflectance spectroscopy. They studied the reduction reaction at a lead cathode in both aqueous and non-aqueous electrolytes. A phase-sensitive detection system was employed by the authors, locked-in to the frequency of the potential modulation. The potential was modulated at 30 Hz between the reference potential of — 1.0 V vs. Ag/AgCl and a more cathodic limit. 

One can reduce the specular reflectance of the display by making its top-surface non-planar, an approach that can also enhance the extraction of light from the device. However, the fact that the emitted light is scattered by the surface structure may have a detrimental effect on the resolution of the display (Nuijs Hoiikx, 1994). 

In this equation, a is the tangential momentum accommodation coefficient, equal to unity for perfectly diffuse molecular reflection and zero for purely specular reflection. In Maxwell s model, MsUp overestimates the real velocity at the wall but leads to a rather good prediction of the velocity out of the Knudsen layer, as represented in Fig. 2. After non-dimensionalization with the characteristic length L, a reference velocity uo, and a reference temperature Tq, Eq. 10 is written as follows ... 

Illumination, diffuse n. Non-specular illumination or non-direct incident light source projected onto the object of observation. Indirect or reflected rays of light are often used as diffuse sources. Also, a scattering lens over a light source will diffuse the rays to reduce specular light. 

Reflectance, non-specular n. Reflectance of radiant flux from a surface at angles other than that of the specular angle, i.e., diffuse reflectance. 

Figure 10.18 Illustration of a ruled diffraction grating. Top grating orders, with m = 0 indicating the non-dispersive specular reflection. Bottom principle of obtaining increased (blazed) grating efficiency...

Sloane and co-workers [129] described a specular reflectance system for the infrared analysis of micro-sized samples. They compare the advantages and limitations of this technique with other micro infrared techniques. Samples are mounted on small metal mirrors (Figure 4.20), which reflect the light beam back through the sample. A transmission spectrum is obtained but the effective path length is twice that of the actual sample thickness and a given absorption band consequently has twice the absorbance obtained by conventional transmission measurements. This system was applied successfully to gas chromatographic fractions, and is particularly useful for the examination of non-volatile liquids such as, for example, dioctyl phthalate. Crystalline solids are easily deposited and... 

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