A feasibility study of soft-tissue imaging based on x-ray wide-angle diffraction contrast has been performed at the medical beamline of the European Synchrotron Radiation Facility (ESRF). The technique employs computed-tomography algorithms to reconstruct from one data set the spatial distribution of several tissues differentiated by their diffraction properties. Radial diffraction profiles are measured in parallel projections from the sample and decomposed into material-selective weighting factors, which form the sinograms for the reconstructions. Attenuation effects--inherent in imaging techniques using scattered radiation--are efficiently corrected for by a ray-tracing method applied to the corresponding absorption image. Images of 7 cm diameter samples composed of fat, bone and muscle were generated at 60 and 80 keV x-ray energy. The highest surface-absorbed dose was 24 mGy, but substantial contrast could still be obtained at 7 mGy, indicating potential applicability in medical imaging. The dominant noise contribution in the images stems from the detection system, pointing to a possible decrease in the surface-absorbed dose for an optimized system of more than a factor of 2.

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Electron momentum spectroscopy has involved the verification of an ab initio model for the target-ion overlap, or Dyson orbital, in a calculation of a high-energy (e,2e) reaction by comparing the resulting cross section with experimental data. We describe an inverse method of extracting the overlap directly from experimental data by using a quantum-mechanically constrained statistical fitting procedure in conjunction with previously verified reaction models.

For the beryllium atom, it is demonstrated that coherent form factors F(k) can be insufficient for inferring the one-particle reduced density matrix (ODM). The description in terms of reciprocal form factors B(s) as the complementary momentum-space property is compared with the results for a least-squares fit to F(k) data. A virtually complete description of the true ODM may be obtained by using a combined data set, as can be shown by representing the ODM in spherically averaged form.

The bonding in a number of σ-bonded diatomic and linear triatomic molecules is interpreted in terms of the one-particle density matrix (ODM) along the bond axis. Special attention is drawn to the off-diagonal contributions of the ODM in a two-dimensional position space representation, which are shown to be indicative of a bonding or antibonding covalent interaction between the atomic centers.