James,
At least for diffraction experiments; the photon scatters off of the
*crystal lattice*, not any individual electron, so you can conserve the
momentum of the photons and the macroscopic crystal without the crystal
recoiling too much.
Best,
Jon
Murray, James W wrote:
Dear All,
While we are talking about X-ray scattering, I have another question. If
an X-ray is elastically scattered from an electron at an angle theta,
its energy is the same is the incoming X-ray. However, the momentum is
not the same, as it now has a component in a perpendicular direction
(see fig below). As I don't believe that the conservation of momentum
really is violated, what is the source of the discrepancy?
Contrast this with most textbook descriptions of Compton scattering,
where the X-ray loses energy and the electron gains kinetic energy.
best wishes
James
X-ray --------> e-
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Dr. James Murray
Biochemistry Building
Department of Biological Sciences
Imperial College London
London, SW7 2AZ
Tel: +44 (0)20 7594 5276
