grazing incidence


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Related to grazing incidence: Glancing angle

grazing incidence

X-rays reflect from surfaces for the same physical reason that light reflects, mainly due to coherent scattering in the surface material. However, since X-ray photon energies are large, the refractive index, n, is slightly less than unity and reflection occurs only up to a critical angle, θ, where cos θ = n. The angle θ is usually small and thus X-ray reflection is only high for rays that graze the surface; hence ‘grazing incidence’. For example θ is about 1° for a gold surface and X-rays of wavelengths of about 0.3 nm (4 keV). θ is proportional to X-ray wavelength and also increases with the atomic number of the reflecting surface.

The space station Skylab was the first space mission to carry a large grazing incidence X-ray telescope, in fact two, both of which produced many high-resolution X-ray images of the solar corona in 1973–74. With two coaxial reflectors (usually a paraboloid/hyperboloid pair), high-quality X-ray images are produced over a field of view of order of the grazing angle. The great potential of such optical systems for cosmic X-ray astronomy was first demonstrated with the flight of a 60-cm diameter grazing incidence telescope on the Einstein Observatory in 1978–81. Subsequently, most X-ray astronomy satellites have employed or will employ this technique.

grazing incidence

[′graz·iŋ ‚in·sə·dəns]
(physics)
Incidence at a small glancing angle.
References in periodicals archive ?
Leroy, "Probing surface and interface morphology with grazing incidence small angle X-ray scattering," Surface Science Reports, vol.
Figure 12 depicts that the values of amplitude ratios [absolute value of ([Z.sub.4])] for transverse force stiffness and thermal contact conductance oscillate up to intermediate range and then decrease in the further range to attain minimum value at grazing incidence. The values for ST1, ST2, NS1, and NS2 decrease in the whole range.
Nordmark, "Bifurcations caused by grazing incidence in many degrees of freedom impact oscillators," Proceedings of the Royal Society London A: Mathematical, Physical and Engineering Sciences, vol.
(9) For the 3[degrees] grazing incidence geometry that was used here, the information depth is about half a micron.
This is incident on a curved mirror, set at grazing incidence, which collimates the beam in the vertical sense.
(95) Study of the adhesion layer formed on brass by SEM and grazing incidence x-ray diffraction.
ImEdge Technology Inc, which has developed edge-lit holography (see HN Vol 7 No 10 & Vol 9 No 1), has been awarded US patent number 6,151,142, entitled Grazing incidence holograms and method of making the same.
Grazing incidence small-angle X-ray scattering (GISAXS) experiments were performed at Elettra-Sincrotrone, Trieste, Italy, on the SAXS beamline [12], using synchrotron radiation with photon energy of 8 keV.
We used a combination of optical microscopy, atomic force microscopy (AFM), and grazing incidence wide-angle X-ray scattering (GIWAXS) to elucidate the morphology at multiple-length scale of spray and spin coated PTB7:P[C.sub.71]BM films.
The case in which [phi]' is equal to 180[degrees] was neglected simply to avoid grazing incidence. As for the range ]180[degrees], 190[degrees]], it was discarded because, with [phi] belonging to [10[degrees], 260[degrees]], the probe would otherwise have an interval in which it is always directly illuminated.
Note that the same assumption of grazing incidence has been made in both (13) and (14).
(2.) Except for grazing incidence, where interference can occur as in Fresnel's mirror experiment.

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