Studying low-energy core-valence transitions with bulk sensitivity using q-dependent NIXS

Absorption-based studies of low-energy atomic edges possess an inherent challenge in distinguishing surface and bulk contributions to the measured signal. The nature of the absorption process itself, being predominantly dipole in character, can also be a limiting factor in understanding electronic structure, particularly for correlated-electron systems. Non-resonant inelastic X-ray scattering (NIXS) provides a complementary means to soft X-ray absorption (XAS) methods in the study of low-energy excitations. The use of higher-energy X-rays (similar to 10 keV) enables bulk-sensitive measurements. Modern instrumentation and synchrotron facilities permit experiments with access to transitions not only in the dipole-transition regime but also those of higher-order. Access to these non-dipole transitions provides an additional perspective into the electronic behavior of materials. Such experiments will be illustrated using rare earth materials and excitations corresponding to M, N and O edges, with emphasis on the sensitivity to 4F-occupation in cerium-based materials. (C) 2010 Elsevier B.V. All rights reserved.