L Journal of Alloys and Compounds 286 (1999) 47–55 Examples of soft X-ray emission and inelastic scattering excited by synchrotron radiation a, b c d e e f * D.L. Ederer , E. Kurmaev , S. Shin , A. Moewes , M. Grush , T.A. Callcott , R.C.C. Perera , g a a h d J. van Ek , S. Stadler , R. Winarski , L.J. Terminello , L. Zhou a Tulane University, New Orleans, LA 70118, USA b Institute of Metal Physics, Russian Academy of Sciences-Ural Division, 620219 Yekaterinburg GSP-170, Russia c Institute of Solid State Physics, University of Tokyo, Tanashi, Tokyo, Japan d Center for Advanced Microstructures and Devices, Baton Rouge, LA 70888, USA e University of Tennessee, Knoxville, TN 37996, USA f Advanced Light Source, Lawrence Berkeley Laboratory, Berkeley, CA 94720, USA g Seagate Technologies, 7801 Computer Ave. S., Bloomington, MN 55435, USA h Lawrence Livermore National Laboratories, Livermore, CA 94551, USA Abstract This paper is a summary of some of the recent activities of our soft X-ray spectroscopy collaboration. We are using soft X-ray emission spectroscopy to probe the electronic properties of matter, emphasizing atoms in the bulk and at interfaces. In particular we have used incoherent photon excitation to obtain a basic understanding of the electronic properties of a wide variety of materials including Sr RuO , 2 4 a new superconductor. In this first copperless perovskite superconductor, we confirmed in-plane oxygen–ruthenium bonding by analysis using calculations and soft X-ray emission spectroscopy and photoelectron spectroscopy. In the case of the sulfides, the sulfur in FeCuS occupies a single site, and the sulfur in CuS forms dimers at two thirds of the sites. This behavior was confirmed by calculation and by measurement of soft X-ray emission spectra excited at different photon energies near the sulfur L absorption edge, and by core 2,3 photoemission measurements. Measurements of this type illustrate the importance of combining SXE and PES measurements with theoretical calculations. The ubiquitous presence of Raman scattering near the 3d and 4d ionization thresholds has been used to elucidate the excitation process in a number of rare earth and transition metal compounds. Such scattering can produce dramatic changes in the emission spectrum that can further the basic understanding of the atomic excitation process in these compounds. Photon-in photon-out soft X-ray spectroscopy is adding a new dimension to soft X-ray spectroscopy by providing many opportunities for exciting research, especially at third generation synchrotron light sources.  1999 Published by Elsevier Science S.A. All rights reserved. Keywords: Soft X-ray spectroscopy; X-ray fluorescence; Raman scattering; Rare-earth materials; Transition metals; Photoelectron spectroscopy; Density of states 1. Introduction at the National Synchrotron Light Source [5]. Similar work was begun in Sweden by a team at Uppsala University led Soft X-ray emission spectroscopy has been applied by Nordgren and his co-workers [6]. Since then several extensively toward the study of materials since the discov- third generation light sources have come on line where the ery of X-rays [1–4]. The topics covered in the 1998 high brightness available at these sources has been put into European Conference on Applications of Synchrotron service studying many different materials and compounds Radiation include a broad spectrum of methods concerning by a number of groups [7–9]. the production and use of X-rays as a scientific tool to The process of photon absorption and photon emission understand the electronic properties of matter. This report is driven by the usual first order process coupling the summarizes some of our activities, which have focused on electron momentum, p, to the vector potential of the photon-in photon-out spectroscopy in the spectral photon photon field, A. Weaker two photon processes involve the energy range below 1 keV. We began our studies in the elastic scattering of photons (Raleigh Scattering) and the 50–300 eV photon energy range a little over a decade ago inelastic scattering of photons (Raman and Compton scattering). Raman scattering was first observed in the soft *Corresponding author. X-ray spectra region three decades ago [10]. These 0925-8388 / 99 / $ – see front matter  1999 Published by Elsevier Science S.A. All rights reserved. PII: S0925-8388(98)00978-5