scholarly journals The Double Diffraction Model for LEED-Intensity Spectra of the Clean Pt(100) Surface

1977 ◽  
Vol 32 (1) ◽  
pp. 28-32 ◽  
Author(s):  
K. Heinz ◽  
P. Heilmann ◽  
K. Müller
Keyword(s):  
Surface Layer ◽  
Reciprocal Lattice ◽  
Normal Incidence ◽  
Second Order ◽  
Double Diffraction ◽  
Multiple Diffraction ◽  
Alternative Models ◽  
Diffraction Model

Abstract The intensity spectra of the superstructure diffraction spots of the clean platinum (100) surface are presented for normal or nearly normal incidence. Their gross features are interpreted in terms of multiple diffraction contributions. It is shown that most of the maxima in the spectra can be explained by double diffraction processes from an idealized pure hexagonal surface layer and quadratic bulk layers. Alternative models in which the surface layer exchanges already all occuring reciprocal lattice vectors would predict additional peaks which, however, do not arise. Therefore superstructure features of the surface layer are assumed to be of second order. Thus double dif­fraction involving only idealized hexagonal and quadratic structures seems to dominate the diffraction behaviour of clean Pt(100).

Interpretation of the Structure of LEED Intensity Spectra in τ-Matrix Approximation for the Platinum (100) Surface

1976 ◽  
Vol 31 (12) ◽  
pp. 1520-1525
Author(s):  
K. Heinz ◽  
N. Lieske ◽  
K. Müller
Keyword(s):  
Normal Incidence ◽  
Computational Effort ◽  
Second Order ◽  
Matrix Approximation ◽  
Double Diffraction ◽  
Scattering Process ◽  
Weak Scattering

AbstractLEED intensity spectra of the clean (00 and ⅕ 0 beams) and cesium covered (½ 0 beam) Pt(100) surface at normal or nearly normal incidence are compared with a double diffraction approach developed for the scattering process. A second order scattering approach is always restricted to cases where strong attenuation or weak scattering of the propagating electrons can be assumed. The comparison shows that many (but not all) intensity features of Pt(100) can be attributed to first and second order scattering processes only. Some of the maxima are likely to represent resonances. For proper assignment an effective inner potential is chosen that accounts for slowly varying dynamical effects as well as distortions of the crystal. The approach reveals only interpretations rather than predictions. However, it needs nearly no computational effort.

Calculation of the Ion Optical Properties of Inhomogeneous Magnetic Sector Fields Part 3: Oblique Incidence and Exit at Curved Boundaries

1959 ◽  
Vol 14 (9) ◽  
pp. 822-827 ◽  
Author(s):  
H. A. Tasman ◽  
A. J. H. Boerboom ◽  
H. Wachsmuth
Keyword(s):  
Oblique Incidence ◽  
Normal Incidence ◽  
Second Order ◽  
Resolving Power ◽  
High Mass ◽  
Curved Boundaries ◽  
Magnetic Sector ◽  
Mass Resolving Power ◽  
Mass Dispersion ◽  
Fringing Fields

In previous papers 1.2we presented the radial second order imaging properties of inhomogeneous magnetic sector fields with normal incidence and exit at plane boundaries. These fields may provide very high mass resolving power and mass dispersion without increase in radius or decrease of slit widths. In the present paper the calculations are extended to include the effect of oblique incidence and exit at curved boundaries. The influence of the fringing fields on axial focusing when the boundaries are oblique, is accounted for. It is shown that the second order angular aberration may Le eliminated by appropriate curvature of the boundaries.

scholarly journals The surface layer integral method for the modelling of the radial gravity gradient component over sea surface

2019 ◽  
Vol 9 (1) ◽  
pp. 127-132
Author(s):  
D. Zhao ◽  
Z. Gong ◽  
J. Feng
Keyword(s):  
Surface Layer ◽  
Integral Method ◽  
Integral Formula ◽  
Radial Component ◽  
Second Order ◽  
Sea Surface ◽  
Gravity Potential ◽  
Gravity Gradient ◽  
Disturbing Potential ◽  
Gradient Component

Abstract For the modelling and determination of the Earth’s external gravity potential as well as its second-order radial derivatives in the space near sea surface, the surface layer integral method was discussed in the paper. The reasons for the applicability of the method over sea surface were discussed. From the original integral formula of disturbing potential based on the surface layer method, the expression of the radial component of the gravity gradient tensor was derived. Furthermore, an identity relation was introduced to modify the formula in order to reduce the singularity problem. Numerical experiments carried out over the marine area of China show that, the modi-fied surface layer integral method effectively improves the accuracy and reliability of the calculation of the second-order radial gradient component of the disturbing potential near sea surface.

AN APPROACH TO INVERSE FILTERING OF NEAR‐SURFACE LAYER EFFECTS FROM SEISMIC RECORDS

Geophysics ◽  
1961 ◽  
Vol 26 (6) ◽  
pp. 754-760 ◽  
Author(s):  
Pierre L. Goupillaud
Keyword(s):  
Surface Layer ◽  
Seismic Reflection ◽  
Normal Incidence ◽  
Resolving Power ◽  
Surface Velocity ◽  
Inverse Filtering ◽  
Near Surface ◽  
Seismic Records ◽  
Stratification Variable ◽  
Velocity Information

This paper suggests a scheme for compensating the effects that the near‐surface stratification, variable from spread to spread, produces on both the character and the timing of the seismic traces. For this purpose, accurate near‐surface velocity information is mandatory. This scheme should greatly reduce the correlation difficulties so frequently encountered in many areas. It may also be used to enhance the resolving power of the seismic reflection technique. The approach presented here is based on the rather restrictive assumptions of normal incidence, parallel equispaced plant reflectors, and noiseless conditions.

The study of second-order contamination caused by multiple diffraction in a Ge(113) monochromator

2001 ◽  
Vol 9 (2) ◽  
pp. 363-371 ◽  
Author(s):  
B. S. Seong ◽  
E. Shin ◽  
C. H. Lee ◽  
V. T. Em ◽  
H. S. Shim
Keyword(s):  
Second Order ◽  
Multiple Diffraction

Analysis of second-order moments in surface layer turbulence in an Alpine valley

2009 ◽  
Vol 135 (644) ◽  
pp. 1750-1765 ◽  
Author(s):  
M. de Franceschi ◽  
D. Zardi ◽  
M. Tagliazucca ◽  
F. Tampieri
Keyword(s):  
Surface Layer ◽  
Second Order ◽  
Alpine Valley

scholarly journals Characterization of Turbulence in the Neutral and Stable Surface Layer at Jang Bogo Station, Antarctica

Atmosphere ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1095
Author(s):  
Mauro Mazzola ◽  
Angelo Pietro Viola ◽  
Taejin Choi ◽  
Francesco Tampieri
Keyword(s):  
Surface Layer ◽  
Large Fraction ◽  
Low Frequency ◽  
Systematic Investigation ◽  
Second Order ◽  
Time Interval ◽  
Stable Conditions ◽  
Stable Surface Layer ◽  
Sonic Anemometers ◽  
Submeso Motions

The availability of 5-year time series of velocity and temperature data from two sonic anemometers installed at Jang Bogo Station, Antarctica, allowed a systematic investigation of the turbulence features in a stable layer affected by submeso motions and characterized by the vertical divergence of some second-order moments for a large fraction of time (quite a non-ideal surface layer). The investigation of the effect of the averaging time interval on the statistics of the second-order moments showed that this is greater for the variances of the velocity components with respect to that for the vertical fluxes. This corresponds to a greater contribution from low-frequency motions. The turbulence statistics were investigated and compared with current literature results in terms of vertical structure, share of energy between horizontal and vertical components, skewness of the vertical velocity and turbulent velocities. As a general result, all the normalized second-order moments show a clear change passing from neutral to stable conditions, passing through the range of bulk Richardson number equal to 0.1–1.

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