A detailed experimental and theoretical study of elastic electron-xenon scattering has been carried out for incident electron energies between 0.67 and 50 eV. The experimental measurements have been conducted using a crossed-beam apparatus and the relative flow technique, while the theoretical calculations are a fully relativistic treatment which also includes the effects of polarization and dynamic distortion. The experimental results (absolute differential cross sections) have been analysed with a relativistic version of a phase-shift analysis program in an effort to extract the low-order phase shifts, including the two spin-orbit components of the low-energy p-wave phase shift, and to derive the total elastic and elastic momentum transfer cross sections. Extensive comparisons between the present measurements and calculations and previous experiment and theory are provided.

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We calculate electron momentum densities of various crystalline solids by employing the linear-muffin-tin-orbital (LMTO) method. We use three levels of approximation to the LMTO: the simplest atomic sphere approximation (ASA), the ASA with overlap correction, and the full-potential (FP) LMTO. Although the band energies calculated using the ASA and the FP-LMTO are practically the same, there is a noticeable difference in the electron momentum densities which is not cured by making a simple overlap correction to the ASA-LMTO method.

The electron momentum density ͑EMD͒ of two different modifications of graphite has been measured and the results of the measurements have been compared with theoretical calculations from three different theories: a full potential linear muffin-tin orbital, a modified augmented plane wave, and a pseudopotential calculation. Experimental results have been obtained by two different methods. The complete three-dimensional EMD is determined by inelastic photon-electron scattering, i.e., by the so-called (␥,e␥) experiment, and by electronelectron scattering, the (e,2e) experiment, cuts in the spectral electron momentum density are studied. For the (␥,e␥) experiment 180 keV synchrotron radiation from the PETRA storage ring at the Deutsches Elektronen-Synchrotron has been used with coincident detection of the recoil electrons. The (e,2e) experiments were carried out at the new (e,2e) spectrometer at the Australian National University using 40 keV primary electron energy and simultaneous detection of the outgoing electrons in an equal energy sharing mode. As samples we have prepared approximately 20 nm thin self-supporting graphite foils either by thermal evaporation ͑TE͒ or by laser plasma ablation ͑LPA͒. They are thin enough to suppress in essence electron multiple scattering. Electron diffraction analysis revealed that the LPA foil contains graphitic basal planes with a random distribution of c axes, whereas the TE foil was strongly c-axis oriented in the sense that the basal planes were parallel to the foil surface. In the analysis of the results special attention was devoted to anisotropies in the EMD revealed by comparison of TE and LPA foils. The (e,2e) measurements showed furthermore a strong orientation dependence of the intensity of and states ͑here we have for comparison additionally measured highly oriented pyrolytic graphite͒. The EMD's obtained by both techniques show anisotropies in the momentum distribution of graphite and are discussed in view of the theoretical results.

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