Compton Scattering: A Theory and Experiments (original) (raw)
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Electron momentum density and Compton profile by a semi-empirical approach
Journal of Physics and Chemistry of Solids, 2015
Here we propose a semi-empirical approach to describe with good accuracy the electron momentum densities and Compton profiles for a wide range of pure crystalline metals. In the present approach, we use an experimental Compton profile to fit an analytical expression for the momentum densities of the valence electrons. This expression is similar to a Fermi-Dirac distribution function with two parameters, one of which coincides with the ground state kinetic energy of the free-electron gas and the other resembles the electron-electron interaction energy. In the proposed scheme conduction electrons are neither completely free nor completely bound to the atomic nucleus. This procedure allows us to include correlation effects. We tested the approach for all metals with Z ¼3-50 and showed the results for three representative elements: Li, Be and Al from high-resolution experiments.
A high-resolution Compton scattering study of hexagonal zinc
Journal of Alloys and Compounds, 2004
The directional Compton profiles (CP) of hcp single crystal of zinc have been measured along the [00·1], [11·0] and [11·1] directions using high energy synchrotron radiation and high-resolution Compton scanning spectrometer at ESRF (Beamline ID15B). The experimental data were compared with corresponding theoretical Korringa-Kohn-Rostoker (KKR) semi-relativistic calculations and previous low-resolution Compton measurements with the use of high-energy ␥ radiation from Cs isotope. Both the experimental and theoretical directional anisotropies of Compton profiles, shows very small anisotropy of the electron momentum density in hexagonal zinc, at most half of that presented in the literature for cubic systems. No sharp fermiology-related features of momentum density in Zn predicted by theory, especially in the momenta region below 1 a.u., are observed.
Compton scattering is a technique for determining the momentum distribution of electrons in condensed matter. Therefore, in the Compton scattering experiment all the available data about the electron's initial state is contained in the distribution of the inelastically scattered radiation, i.e. the Compton profile. However, before the data can be interpreted, a series of energy dependent corrections have to be applied. In this paper, general aspects of the Compton Scattering theory are introduced. Data analysis procedure for the γ-ray experiment is outlined and the sensitivity of these corrections on the quality of the final results is discussed.
Compton Scattering of X Rays from Bound Electrons
Physical Review A, 1970
Exact and approximate methods for determining the momentum distribution of electronic systems from Compton scattering measurements are presented. The method used previously to analyze Compton scattering measurements, the impulse approximation (IA), is derived from first principles, and its accuracy is compared with the exact calculations for Compton scattering from a hydrogenic system. It is shown that the IA gives very accurate results for weakly bound electrons and that exact calculation may only be necessary to subtract out the contributions to Compton scattering from deeply bound core electrons. Experimental results for Compton scattering from helium are presented as a test of the above ideas. Analyzing the results of the experiment in the IA gives a momentum distribution for the weakly bound helium electrons which is in excellent agreement with the momentum distribution obtained from Clementi Hartree-Fock wave functions.
Hybridization Effects in Solids Studied by Compton Scattering
Le Journal de Physique Colloques, 1987
Nous prksentons une s6rie de mesures de profils Compton sur des cristaux de LiH et de LiC6. La comparaison avec les profils calcul6s permet de tester la qualit6 des fonctions d'onde du systkme, et par 18 de v6rifier si la base de fonctions d'onde utilist?es pour cr6er les orbitales prend en compte toutes les hybridations 6ventuelles.
Compton profiles of heavy atoms by inelastic proton-electron scattering
Zeitschrift f�r Physik B Condensed Matter, 1988
So-called ion Compton profiles can be obtained if the recoiling electron after an inelastic ion-electron encounter is observed and energy analyzed. Electron recoil spectra induced by 21 MeV protons passing through thin Ag and Au foils are measured. It is demonstrated that the method is accurate enough to extract valence Compton profiles of Ag and Au from the data. The advantages and disadvantages compared to inelastic y-or electron-electron scattering are discussed. It turns out that this new method for the measurement of Compton profiles is especially suitable for heavy elements and very thin or small targets (e.g. clusters).
The refinement of anisotropic Compton profiles and of momentum densities
Acta Crystallographica Section A Foundations of Crystallography, 1995
A very simple relationship between momentum density and the Fourier transform of the population matrix is derived, valid for the representation of the electronic structure of a solid in a given atom-like basis set. This expression allows for the direct refinement of experimental anisotropic Compton profiles: the parameters are the coupling coefficients between various atomic functions and adjustable constants describing the radial part of atomic functions. In the case of unfilled bands, the shape of the Fermi surface can be refined as well. A simple ionocovalent model is proposed for LiH crystals, for which many anisotropic Compton profiles have been measured. The result of the refinement is very satisfactory, leading to a fair description of the anisotropies of the momentum density. The agreement between theory and experiment is as good for this simple model (with ony four parameters) as for a sophisticated band-structure calculation. Possible extensions are presented.
High resolution Compton scattering study of molybdenum
Journal of Physics and Chemistry of Solids, 2001
In this paper directional Compton pro®les of Mo are presented and the results compared with LCGO and APW model calculations. Both electronic structure models describe qualitatively the anisotropy of the electron momentum distribution, which is in¯uenced by the Fermi surface topology. However, the absolute pro®les indicate that electron±electron correlation effects are inadequately described within the local density approximation. q