Eur. Phys. J. Special Topics 208, 75-87 (2012)
https://doi.org/10.1140/epjst/e2012-01608-1

Regular Article

Anisotropy in Borrmann spectroscopy

¹ Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK
² Deutsches Elektronensynchrotron DESY, FS-DO, Notkestraße 85, 22607 Hamburg, Germany
³ A. V. Shubnikov Institute of Crystallography, 119333 Moscow, Russia

^a e-mail: steve.collins@diamond.ac.uk

Received: 19 December 2011
Revised: 23 March 2012
Published online: 15 June 2012

Abstract

In this paper we introduce Borrmann Spectroscopy as a method for measuring X-ray absorption spectra under conditions of an exotic wave field, namely, a coherent superposition of two plane waves. The essential features of the Borrmann Effect (also known as anomalous transmission) are outlined. We show that the Borrmann Effect can lead to a very strong relative enhancement of quadrupole absorption. After describing some early results in this field, and some general considerations of multiple-wave absorption, we contrast recent results on anisotropy in Borrmann spectroscopy with normal absorption. Despite the qualitative success of a simple model for quadrupole enhancement, temperature dependence and anisotropy, a general theory of the Borrmann Effect is required which includes anisotropic and non-dipolar scattering. We outline some first steps towards such a theory.