X‐ray natural circular dichroism in langasite crystal. (12th December 2017)

• Record Type: Journal Article
• Authors: Oreshko, Alexey P.; Ovchinnikova, Elena N.; Rogalev, Andrei; Wilhelm, Fabrice; Mill, Boris V.; Dmitrienko, Vladimir E.
• Is Part Of: Journal of synchrotron radiation. Volume 25:Part 1(2018)
• Page Start: 222
• Page End: 231
• Publication Date: 2017-12-12
• Subjects: optical activity -- circular dichroism -- X‐ray absorption spectra; Synchrotron radiation -- Periodicals; Free electron lasers -- Periodicals; 539.73505
• DOI: 10.1107/S1600577517015387
• Languages: English
• ISSNs: 0909-0495

Abstract

Abstract : The X‐ray natural circular dichroism of langasite crystal La3 Ga5 SiO14 near the Ga K ‐edge is described in terms of the gyration tensor formalism. The experimental spectra are compared with the results of ab initio calculations that, for the first time, have allowed one to disentangle the contributions from Ga atoms in different Wyckoff positions. Abstract : Optical activity in the X‐ray range stems from the electric‐dipole–electric‐quadrupole interference terms mixing multipoles of opposite parity, and can be observed exclusively in systems with broken inversion symmetry. The gyration tensor formalism is used to describe the X‐ray optical activity in langasite La3 Ga5 SiO14 crystal with the P 321 space group. An experimental study of the X‐ray natural circular dichroism (XNCD) near the Ga K ‐edge in La3 Ga5 SiO14 single crystal was performed at ESRF beamline ID12, both along and perpendicular to the crystal optical axis. The combination of the quantum mechanical calculations and high‐quality experimental results has allowed us to separate the contributions into X‐ray absorption and XNCD spectra of Ga atoms occupying three distinct Wyckoff positions.