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Started by Guido Pascale
Wed, 23 Aug 2000 00:00
x-rays: explain diffraction vs coherent scatter
Author: Guido Pascale
Date: Wed, 23 Aug 2000 00:00
Date: Wed, 23 Aug 2000 00:00
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Within the medical imaging regime, the dominant x-ray interaction processes are the photoelectric effect, the Compton (incoherent), and Rayleigh (coherent) scatter. The Rayleigh contribution is usually negligible, yet for lower x-ray photon energies and lower Z (atomic number) absorbers, the Rayleigh component may exceed the Compton component. Would someone please explain is the difference between Rayleigh (coherent) scatter, and what is generally regarded as x-ray diffraction (say, Bragg diffraction)? Thanks in advance, Guido Pascale Sent via Deja.com http://www.deja.com/ Before you buy.
Re: x-rays: explain diffraction vs coherent scatter
Author: Cl.Mass�
Date: Mon, 28 Aug 2000 00:00
Date: Mon, 28 Aug 2000 00:00
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Guido Pascale wrote: > Would someone please explain is the difference between Rayleigh > (coherent) scatter, and what is generally regarded as x-ray diffraction > (say, Bragg diffraction)? There is none. Bragg diffraction is the result of the interference between outcoming Rayleigh scattered x-ray. -- ~~~~ %20clmasse@free.fr%20 LPF God is logically self-inconsistent.
Re: x-rays: explain diffraction vs coherent scatter
Author: L. D. Marks
Date: Thu, 31 Aug 2000 18:58
Date: Thu, 31 Aug 2000 18:58
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While it is true that there is no difference between Rayleigh and Bragg scattering in many respects, this is only part of the answer. Bragg diffraction as used for x-ray diffraction refers primarily to the case when the wave scattered from different regions add coherently to give a large nett intensity. Rayleigh scattering is, I think, more for the case when the scattering from different regions adds incoherently. A loose analogy would be to compare Rayleigh scattering to what one has from an amorphous material, versus Bragg diffraction from a crystal. -- Laurence Marks Department of Materials Science and Engineering Northwestern University fax: (847) 491-7820 mailto:L-marks@northwestern.edu http://www.numis.nwu.edu
Re: x-rays: explain diffraction vs coherent scatter
Author: Rainer
Date: Fri, 01 Sep 2000 21:17
Date: Fri, 01 Sep 2000 21:17
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Still Rayleigh is the origin of Bragg. The first is the one-photon one-atom interaction the second the experiment with an entity of photons interacting with an entity of atoms. You get Bragg reflexes when the atoms are ordered. Otherwise you get kind of specles. Rainer In article <39AE8396.15629746@nwu.edu>, L-marks@nwu.edu wrote: > While it is true that there is no difference between Rayleigh and Bragg > scattering in many respects, this is only part of the answer. Bragg > diffraction > as used for x-ray diffraction refers primarily to the case when the wave > scattered from different regions add coherently to give a large nett > intensity. > Rayleigh scattering is, I think, more for the case when the scattering > from different regions adds incoherently. A loose analogy would be to > compare Rayleigh scattering to what one has from an amorphous material, > versus Bragg diffraction from a crystal. > > -- > Laurence Marks > Department of Materials Science and Engineering > Northwestern University > fax: (847) 491-7820 > mailto:L-marks@northwestern.edu > http://www.numis.nwu.edu > > -- Platzegel 21 B-4721 Kelmis Belgium Sent via Deja.com http://www.deja.com/ Before you buy.
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