High-resolution inelastic X-ray scattering I: Context, spectrometers, samples, and superconductors

Abstract

This paper reviews nonresonant, meV-resolution inelastic x-ray scattering (IXS), as applied to the measurement of atomic dynamics of crystalline materials. It, in conjunction with a companion paper on theory and calculations (Part II), is designed to be an introductory, though in-depth, look at the field for those who may be interested in performing IXS experiments or in understanding the operation of IXS spectrometers or even those desiring a practical introduction to harmonic phonons in crystals at finite momentum transfers. The treatment of most topics begins from ground level, with an emphasis on practical issues, as they have occurred to the author in 15 years spent introducing meV-resolved IXS to Japan, including designing and building two IXS beamlines, spectrometers and associated instrumentation, performing experiments, and helping users. After a short introduction to the broader field of IXS, this paper, Part I, discusses the relative merits of IXS as compared to other methods of investigating atomic dynamics, especially inelastic neutron scattering (INS). A very brief overview of spectrometer operation and the types of spectra observed is also given. The paper then focuses on the main issues relevant for spectrometer design, including a brief survey of relevant formulas from dynamical diffraction and an in-depth discussion of how various design issues have been addressed in the different types of operating spectrometers, including spectrometers using spherically figured analyzers and the relatively new "post-sample-collimation" (PSC) systems. Finally, there is discussion of the types of experiments that have been carried out with a brief discussion of the many types of crystalline samples that have been investigated and detailed discussion on measurements of superconductors.