Pure Reflection Research Articles

Comments on analyses of reflection gratings

The descriptions of diffraction by pure reflection gratings (fringes parallel to surfaces) and by reflection gratings with slanted fringes are clarified. The rigorous coupled-wave analysis, the chain-matrix analysis, and the new method presented by Zylberberg and Marom [ J. Opt. Soc. Am.73, 392 ( 1983)] are compared and their regions of applicability determined. Zylberberg and Marom refer to their method as a coupled-wave analysis, a description that is inconsistent with previous use of this terminology.

逆浸透膜の性能評価法

The method of quantitative qualification of reverse osmosis membranes from experimental data by using appropriate transport equations and defining membrane characteristics as transport parameters, such as pure water permeability, solute permeability and reflection coefficient is presented. Thereby the importance and the effect of concentration polarization phenomena are stressed, and its correction methods are shown. The character of membranes deteriorate gradually with time by various causes, such as compaction by the mechanical pressure, deposition of suspended matters or high molecular weight solutes on the membrane surface and chemical adsorption, oxidation or hydration of membrane materials. The quantitative estimation of some of such effects are discussed.

Enhanced nuclear resonance scattering in dynamical diffraction of gamma rays

The angular and energy dependence of the dynamical diffraction of gamma rays was studied experimentally in the symmetric Bragg case. Mossbauer diffraction spectra were measured with high angular resolution in pure nuclear Bragg reflection of a nearly perfect 57FeBO3 single crystal. In the spectrum taken at the exact Bragg position, very broad hyperfine resonance peaks were observed. In the spectra just above and below the Bragg angle the reflection peaks were much smaller and were shifted to energy positions above and below resonance respectively. The results were interpreted by means of the dynamical theory and compared with computer calculations. The measurements represent the first direct observation of the enhancement of nuclear resonance scattering in the case of a thick crystal reflection. Furthermore the angular dependence of the resonance scattering by a perfect single crystal has been measured for the first time.

ENHANCED NUCLEAR RESONANCE SCATTERING IN DYNAMICAL DIFFRACTION OF GAMMA-RAYS

ibstract. The angular and energy dependence of the dynamical diffraction of gamma rays was studied experimentally in the symmetric Brag case. Mossbauer diffraction spectra were measured with high angular resolution in a pure nuclear Bragg reflection of a nearly perfect 57FeB0, single crystal. In the spectrum taken at the exact Bragg position, very broad hyperfine resonance peaks were observed. In the spectra just above and below the Bragg angle the reflection peaks were much smaller and were shifted to energy positions above and below resonance respectively. The results were interpreted by means of the dynamical theory and compared with computer calculations. The measurements represent the first direct observation of the enhancement of nuclear resonance scattering in the case of a thick crystal reflection. Furthermore the angular dependence of the resonance scattering by a perfect single crystal has been measured for the first time. Soon after the discovery of the Mossbauer effect the dynamical diffraction of gamma radiation by a regular ensemble of resonant nuclei was considered theoretically. First the diffraction of gamma rays incident on a thin perfect single-crystal film near the Bragg angle was studied (Trammell 1961). It was found that in this case the halfwidth of the resonance scattering is larger than for an isolated nucleus and increases with the thickness of the crystal film. The energy broadening of the resonance scattering was called the enhancement effect. A general treatment of the dynamical diffraction of resonant gamma rays in thick perfect single crystals was given for the hue case (Afanas’ev and Kagan 1965) and also for the Bragg case (Kagan et al1968). In the latter paper it was shown that in the case of a Bragg reflection by an infinitely thick perfect crystal, under certain conditions, an angular position can be found where the reflection becomes total in spite of the presence of a strong inelastic channel and independent of the energy distance from resonance. In the region around this angular position the reflectivity falls off rapidly. Thereby the reflectivity remains unchanged when the energy distance from resonance and the angular deviii:ion are both changed in sign. Also the Bragg reflection by thin perfect crystals was treated in a general way (Hannon and Trammell 1969). The contributions of other authors may be found summarised in review articles (Belyakov 1975, Champeney 1979). Recently the problem of filtering of

Impedance-Matched Grazing-Incidence Films: Pure Nuclear Reflections, Resonant Filtering of Synchrotron Radiation, and X-Ray Interferometry

The purpose of the Letter is to point out the possibility of a new interference technique in x-ray and $\ensuremath{\gamma}$-ray optics---the simple idea of impedance-matched grazing-incidence films---and to discuss applications to pure nuclear coherent reflections, resonant filtering of synchrotron radiation, and x-ray interferometry.

Discussion on “Diffraction response for nonzero separation of source and receiver,” by John R. Berryhill (GEOPHYSICS, October 1977, p. 1158–76, and Discussion on “Diffractions for arbitrary source‐receiver locations,” by A. W. Trorey (GEOPHYSICS, October 1977, p. 1177–82)

Study of simple synthetic seismograms convinced both authors that the diffracted pulse shape shows virtually no variation with source‐receiver offset if the midpoint is held constant. First, I wish to corroborate their findings by means of a simple example and at the same time suggest that conclusions of both authors apply strictly only to planar (and planar dipping) reflectors. Secondly, I wish to show that because of the invariant behavior of the pure diffraction pulse and because of the equally invariant behavior of the pure reflection pulse, the shape of the reflected pulse for depth points close to the edge of the reflector can not be offset invariant.

A RMEED and SEM investigation of metal oxidation phenomena

We have recently completed an in-situ study of the reaction of copper thin films at low oxygen pressures (10-5 torr) and relatively high temperatures (500-700°C).These conditions allow convenient observation over reasonably short reaction times in our UHV RMEED/SEM instrument(1).Epitaxially grown (111) copper films of approximately 100nm thickness were prepared in a conventional HV system and placed in the UHV system as produced on their mica substrates. Epitaxy was confirmed by TED/TEM on pieces of the film which were stripped off the substrate and by the electron channeling patterns observed in the SEM. Initial treatment in the UHV system included annealing at 300°C for several hours and a final anneal at 500°C for one hour. In one case the film was sputter cleaned with a 700eV argon ion beam between the two annealing processes. Some oxide nuclei of various sizes were observed after this treatment.After the initial cleaning pure copper reflection diffraction patterns as in Fig.1 were recorded up to the sixth order.

Surface modes in electron plasmas

Density fluctuations in a semi-infinite collisional electron plasma are studied using "two-stream" distribution functions. Microscopic boundary conditions, imposed separately upon each of the velocity streams, are formulated with the inclusion of both specular reflection and diffuse scattering contributions. The strong damping of surface modes noted by previous investigators is shown to be, in part, a consequence of the use of pure specular reflection boundary conditions. With increasing diffuse scattering contributions the surface modes are seen to become an enhanced and identifiable spectral feature.

Neutron Scattering for Antiferromagnetic γFe0.7Ni0.15Cr0.15Alloy (Non Magnetic Stainless Steel)

The antiferromagnetic structure of a γFe 0.7 Ni 0.15 Cr 0.15 has been investigated with a triple axis neutron spectrometer. The magnetic scattering has been observed at 4.2 K around both the (110) and (001) reciprocal lattice points. It has been found that the 110 scattering is a pure Bragg reflection which disappears at T N of 26±1 K. On the other hand, the 001 scattering was found to be purely quasi-elastic scattering, the profile of which depends strongly on the incident neutron energy. The results suggest that γ-Fe-Ni-Cr has a long range antiferromagnetic order of γ-Mn type with a sublattice magnetic moment of 0.3±0.1 µ B per atom aligned along the [001] direction. The components of spins perpendicular to the [001] axis have only a short range correlation and they fluctuate in time even at 4.2 K. The results for neutron scattering in a magnetic field of 47 kOe suggest that the induced moment can be interpreted by the canting of the antiferromagnetic spins in the field direction.

Spectroscopy of R Monocerotis and NGC 2261

view Abstract Citations (30) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectroscopy of R Monocerotis and NGC 2261. Stockton, A. ; Chesley, D. ; Chesley, S. Abstract Spectrograms obtained in early 1974 of NGC 2261, the cometary nebula associated with R Mon, show a variation in the velocity of the reflected absorption spectrum as a function of distance from R Mon. The emission lines in the reflection spectrum show no signiflcant variation; thus differential motions within the nebula cannot be responsible for the absorption4ine variation. The effect is attributed instead to time variations in the absorption shell around R Mon, in conjunction with the differences in total light travel times for light scattered from different portions of the nebula. Over the course of approximately one year, the expansion velocity of the shell dropped from 260 km 1 to 135 km 1 The [0 II] A3727 doublet reported by Kazaryan and Khachikyan in the spectrum of NGC 2261 does not arise within the nebula, but results from the projection of the outer parts of the H II region surrounding the nearby OS star, S Mon, onto NGC 2261. All of the differences observed between the spectra of R Mon and NGC 2261 can be interpreted in terms of (1) variations in the spectrum of R Mon and time delay in the light reaching us via NGC 2261, or (2) contamination of the spectrum of NOC 2261 by lines from the H II region around S Mon. Thus, the interpretation of NGC 2261 as a pure reflection nebula is reaffirmed. Subject headings: nebulae, individual - stars, individual Publication: The Astrophysical Journal Pub Date: July 1975 DOI: 10.1086/153703 Bibcode: 1975ApJ...199..406S Keywords: Absorption Spectra; Astronomical Spectroscopy; Line Spectra; Nebulae; Emission Spectra; Gas Ionization; H Alpha Line; H Beta Line; Spectrum Analysis; Astronomy full text sources ADS | data products SIMBAD (2)

Steady One-Dimensional Radiative Heat Transfer with Emission, Reflection and External Radiation

This paper deals theoretically with a radiative heat transfer through an absorbing-emitting medium which occupies a semi-infinite space bounded by a plane wall. A steady one-dimensional problem is considered. The medium is assumed to be grey and to be in a local thermodynamic equilibrium. Effects due to the emission from the wall, specular and diffuse reflection at the wall and external beam radiation through the wall are considered in contrast with the Milen problem, in which no radiation comes into the medium through a purely transparent boundary. The general solution is obtained. The solution is studied in detail in five special cases to show each effect of these boundary conditions. They are the cases of pure emission, pure beam radiation input, pure reflection, a uniform asymptotic field and emission accompanied by diffuse reflection. In the second case, a localized temperature change is found in the neighbourhood of the wall, even when the asymptotic field has a uniform temperature.

Direct Quantitative Photometry on Thin Layer Chromatograms

AbstractThe principal methods for the direct photometric evaluation of thin layer chromatograms are discussed with the aid of examples. Since light is strongly scattered by TLC adsorbents, absorption measurements in reflection are preferable to transmission measurements. In the reflection measurements, an approximation method for the Kubelka‐Munk function leads to satisfactory straight calibration lines. The working range for quantitative reflection measurements is in the μg range, and the detection limit is of the order of 10−8g. The standard deviation for spots of equal concentration is less than ±1%. The signal‐to‐background ratio is improved by simultaneous measurement of reflection and transmission. The measurement of diminution in fluorescence (“fluorescence quenching”) is found to be less sensitive than the reflection at the absorption maximum. However, combined measurement of the reflection and the diminution of fluorescence gives an increase in sensitivity as compared to pure reflection measurements. As in solution photometry, fluorescence measurements are generally much more sensitive than absorption measurements. The working range is normally in the ng region, and the detection limit is around 10−11g. All the investigations described in this paper were carried out on the Zeiss chromatogram spectrophotometer.

La contradicción: ¿vicio formal o cifra de contenido?

Resumen

Über den einfluss der polykristallinen struktur auf den elektrischen widerstand aufgedampfter nickelfilme

The thickness dependence of the electrical resistance of nickel films evaporated at 77 °K under ultrahigh-vacuum conditions on glass substrates can be explained qualitatively by means of the Fuchs-Sondheimer theory of diffuse electron scattering at the film surfaces. On the other hand, it is possible to describe the experimental results by assuming a pure specular reflection of the conduction electrons at the film surfaces and simultaneously taking into account the crystallite boundary scattering.

Determination of the specular reflection coefficient of conduction electrons in Zn whiskers atT=4.2�K

The influence was studied of the transverse dimensions of Zn single crystals in the form of whiskers and thin platelets on their specific resistance atT=4.2°K. The thickness of the specimens measured ranged from 10 µm to 0.2 µm. With a decreasing thickness of the specimens the specific resistance increased considerably. Under the assumption that for a pure diffuse reflection of electrons on the specimen boundary the product (ρ∞ ·d∞) in a bulk specimen is equal to 1.8×10−11 Ωcm2 for a crystallographic orientation corresponding to whiskers, and 2.2×10−11 Ωcm2 for a crystallographic orientation corresponding to platelets, a specular reflection coefficientp approximately equal top=0.6 was calculated for both whiskers and platelets.

Heat transfer from a viscous nongray radiating shock layer.

component. The behavior of real surfaces at large angles of incidence would be of extreme interest in view of off-specular peaks which have been studied by Torance, Sparrow, and Birkebak, e.g., Ref. 5. The significant point to be made is that photon-induced forces cannot be predicted satisfactorily for real surfaces that have combined diffuse and specularly reflecting properties by using ideal reflectance models. Lastly, a few remarks are in order on possible changes in the result for solar energy that could be experienced if experimental reflectance data were available to permit relaxation of the assumption that reflection occurs only in the plane of incidence. The same total reflected energy is assumed as follows: 1) Diffuse model. Pz and Py would be zero and Px would not be changed in magnitude. 2) Specular model. By definition of pure specular reflection, there would be no change in results and Py = 0. 3) Real surface model. The general trend would be to increase the diffuse characteristics of the reflected energy. Assuming the same orientation of axes and a reflection func-

Nature of the polarizing effect of diffraction gratings

The polarization of electromagnetic radiation upon diffraction from a grating is basically determined by the boundary conditions which hold at its surface for the tangential components of the E and H vectors [1]. In the case of a metal grating with steplike groove lines, a component with the E vector parallel to the grooves experiences the greatest deviation from the classical theory of diffraction. For this component, the maximum of the reflection coefficient is displaced from the direction of pure mirrorlike reflection from the faces of the grooves, this displacement tending toward the short-wave region [2]. For this polarization state, the spectral intensity distribution curve in the region of the maximum has a shape similar to that calculated according to classical diffraction theory. In contrast to this, the shape of the curve for the component perpendicular to the grooves is often rather dissimilar.

Extinction effects in neutron scattering from single magnetic crystals

Results arising from the treatment of magnetic scattering of neutrons, taking due account of the possibility of polarization of the neutron beam, indicate that the usual expressions for primary and secondary extinction must be modified in certain cases. Extinction, particularly primary extinction, will be generally more severe for reflections which have both nuclear and magnetic contributions than for either pure nuclear or pure magnetic reflections. Formulas and curves are presented for primary and secondary extinction corrections which are applicable to both magnetized and unmagnetized ferromagnetic or antiferromagnetic crystals. Some of the results obtained may be conveniently used to determine relative amounts of primary and secondary extinction, and consequently both mosaic block size and angnlar distribution. Many of the calculations are of interest in predicting the effects of extinction on experiments designed either to produce or use polarized neutron beams. The precession of the neutron polarization axis about the magnetic axis can affect the reflected intensity if extinction is severe. This effect is discussed briefly and is shown to be serious only for magnetized crystals. The appendix discusses the necessary changes in the scattering formulas if all the spins in the unit cell do not lie along a unique magnetic axis.more » (auth)« less