On jeudi 31 mai 2007, Murray, James W wrote: > 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?
You cannot correctly describe photon-electron interactions using classical mechanics. One reason is that the energy (among over properties) of the electron is quantified, so the photon cannot transfer an arbitrary amount of energy/momentum to the electron. So you'd have to consider the interaction between the photon and everything it is bound with (atom, lattice..) Incidentally, I think the classical delta(lambda) formula for Compton scattering is computed for a _free_ electron. Vincent -- Vincent Favre-Nicolin Université Joseph Fourier