ABSTRACT
IXS has matured into a valuable scattering technique, especially in cases where inelastic neutron scattering (INS) techniques are difficult to apply. This concerns, for example, studies on disordered systems such as liquids and glasses at small momentum transfers (Q) and high energy transfers (E)—a portion of the Q−E space that is often unreachable due to kinematic limitations. For the large variety of studies on simple, associated and metallic liquids, polymers, biological aggregates, and glasses, the interested reader is referred to several reviews [9-12]. A second specific case, relevant in the present context, concerns the necessary sample volume in order to perform an INS or IXS experiment. Although INS experiments need sample volumes of typically several mm3, IXS measurements can be performed utilizing volumes several orders of magnitude smaller (10-5 –10-4 mm3). This opens up possibilities to study materials only available in very small quantities and/or their investigation in extreme thermodynamic conditions, most notably at very high pressures using diamond anvil cell techniques [13,14], as well as experiments in near-surface-sensitive geometry [15,16]. In the past 20 years, a multitude of materials ranging from elemental solids-mostly at high pressures (and temperatures)—over large bandgap materials to biological systems were investigated. The study of correlated electron systems, and in particular superconductors, is an active field of research, since quite often a sufficient single-crystalline quality and homogeneous doping can only be obtained for tiny crystals, by far too small to be studied by INS. Recent reviews give a concise overview of work performed on crystalline materials [10,17,18,]. The chapter is structured as follows: Section 6.2 provides the general formalism; Section 6.3 discusses the experimental principles; and Sections 6.4-6.6 discuss representative examples of recent research conducted on beamline ID28 and BM01A at the ESRF, and beamline X06SA at the Swiss Light Source or SLS: the efficient mapping of phonon dispersion sheets by a multianalyzer crystal spectrometer [19], virtues and strength of combining diffuse scattering (DS) and IXS studies [20-22] and finally the discussion of a recently proposed methodology to extract the complete, Q-and E-resolved, lattice dynamics from polycrystalline IXS data [23,24].
