Compton Scattering

This method was always considered a competitive method to positron annihilation (PA) where the "test particles" injected into the probe are high-energetic x or gamma photons. The experimental investigation of these photons scattered by the electrons of the sample leads to so-called Compton profiles which can be considered one-dimensional projections of the electron momentum density (EMD). Obviously, the greatest advantage of CS compared to PA is the fact that since no charged particles go in or out of the sample, the results of this method are not complicated by "enhancement effects" as mentioned before. On the other hand, for a long time, the usefulness of CS has been strongly limited by a lack of adequate momentum resolution (typically 0.4-0.5 a.u. in comparison with 0.07 a.u. for the PA spectroscopy). However, since about 1985, the availibility of high energy, high intensity sychrotron sources decisively improved the momentum resolution of CS and made this method a realistic alternative to PA both for Fermi surface and EMD studies. These new "high-resolution Compton experiments" yield high-quality Compton profiles including a plenty of details and led to a real "boom" of corresponding theoretical investigations. Similar to positron annihilation, Compton scattering is very attractive to theorists because of the fact that almost all methods of theoretical solid state physics are to be used for a proper description of Compton profiles (Green's functions and Feynman diagrams, static and dynamical dielectric matrices, self-energy and GW methods etc.), demanding high-level work from the physical, mathematical and computational point of view.

After intensive preparations during the recent year 2001, I plan to enter the Compton scattering field in the immediate future.

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