The sequential derivation of an expression that describes an X-ray natural circular dichroism (XNCD) signal in the most general case is performed. The obtained expression is used as a basis to consider XNCD signals and their structural origins in copper metaborate CuB2O4 crystals at an incident radiation energy near the K absorption edge of copper and lanthanum–gallium silicate La$_3$Ga$_5$SiO$_{14}$ crystals at an incident radiation energy near the K absorption edge of gallium. It has been demonstrated that the measurements of circularly polarized X-ray absorption spectra in combination with corresponding first-principle calculations provide an efficient method for studying the contributions of crystallographically non-equivalent atoms to the X-ray optical activity of crystals.
78.20.Ek Optical activity
78.70.Dm X-ray absorption spectra
$^1$Department of Solid State Physics, Faculty of physics, Lomonosov Moscow State University, chair of Condensed Matter Physics.\
$^2$FSRC “Crystallography and Photonics” of RAS
Science News of the Faculty of Physics, Lomonosov Moscow State University
This new information publication, which is intended to convey to the staff, students and graduate students, faculty colleagues and partners of the main achievements of scientists and scientific information on the events in the life of university physicists.