Incidence grazing

The actual structure at a vapor-liquid interface can be probed with x-rays. Rice and co-workers [72,73,117] use x-ray reflection to determine the composition perpendicular to the surface and grazing incidence x-ray diffraction to study the transverse structure of an interface. In a study of bismuth gallium mixtures. 

Since the development of grazing incidence x-ray diffraction, much of the convincing evidence for long-range positional order in layers has come from this technique. Structural relaxations from distorted hexagonal structure toward a relaxed array have been seen in heneicosanol [215]. Rice and co-workers combine grazing incidence x-ray diffraction with molecular dynamics simulations to understand several ordering transitions [178,215-219]. 

Grazing incidence excitation of a fluorescent probe in a phospholipid monolayer can also be used to indicate order. The collective tilt of the molecules in a domain inferred from such measurements is indicative of long-range orientational order [222]. 

Madey and co-workers followed the reduction of titanium with XPS during the deposition of metal overlayers on TiOi [87]. This shows the reduction of surface TiOj molecules on adsorption of reactive metals. Film growth is readily monitored by the disappearance of the XPS signal from the underlying surface [88, 89]. This approach can be applied to polymer surfaces [90] and to determine the thickness of polymer layers on metals [91]. Because it is often used for chemical analysis, the method is sometimes referred to as electron spectroscopy for chemical analysis (ESCA). Since x-rays are very penetrating, a grazing incidence angle is often used to emphasize the contribution from the surface atoms. 

HEED High-energy electron diffraction [104] Diffraction of elastically back-scattered electrons (-20 keV, grazing incidence) Surface structure... 

IRRAS Infrared reflection- Grazing-incidence polarized Enhanced sensitivity... 

There is a fair amount of work reported with films at the mercury-air interface. Rice and co-workers [107] used grazing incidence x-ray diffraction to determine that a crystalline stearic acid monolayer induces order in the Hg substrate. Quinone derivatives spread at the mercury-n-hexane interface form crystalline structures governed primarily by hydrogen bonding interactions [108]. 

Melroy O R, Toney M F, Borges G L, Samant M G, Kortright J B, Ross P N and Blum L 1989 An In situ grazing incidence x-ray scattering study of the initial stages of electrochemical growth of lead on silver(111) J. Electroanal. Chem. 258 403-14... 

The dispersing element is a diffraction grating preferably used under conditions of grazing incidence (6 in Equation 3.9 about 89°) to improve the reflectance. The grating may also be concave to avoid the use of a focusing mirror. 

The development of mote intense sources (eg, plasma sources, soft x-ray lasers, and synchrotron sources) has made possible highly effective instmments both for x-ray microscopy and x-ray diffraction on a few cubic nanometer sample. The optical problem of focusing x-rays is accompHshed by the use of zone plates or by improved grazing incidence or multilayer reflectors. 

M. F. Toney and S. Brennan. Structural Depth Profiling of Iron Oxide Thin Films using Grazing Incidence Asymmetric Bra X-ray DiflFraction. J. Appl. Phys. 65J 4763, 1989. 

The primary X-ray beam is directed onto the solid surface in grazing incidence. The angle of incidence is kept below the critical angle at which total reflection occurs. The critical angle is given by... 

Grazing Incidence X-Ray Diffraction Grazing Incidence X-Ray Diffraction Double Crystal Diffractometer... 

With p-polarized radiation and incident angles near grazing incidence an increase in sensitivity of approximately a factor of 25 can be achieved in comparison with transmission experiments [4.265]. This advantage is reduced to a factor of 17 for a more realistic experimental situation in which the spread of incident angles is ca. 5° at approximately 85°. 

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