X-ray Birefringence: A New Strategy for Determining Molecular Orientation in Materials

Abstract

While the phenomenon of birefringence is well-established in the case of visible radiation and is exploited in many fields (e.g., through the use of the polarizing optical microscope), the analogous phenomenon for X-rays has been a virtually neglected topic. Here, we demonstrate the scope and potential for exploiting X-ray birefringence to determine the orientational properties of specific types of bonds in solids. Specifically, orientational characteristics of C-Br bonds in the bromocyclohexane/thiourea inclusion compound are elucidated from X-ray birefringence measurements at energies close to the bromine K-edge, revealing inter alia the changes in the orientational distribution of the C-Br bonds associated with a low-temperature order-disorder phase transition. From fitting a theoretical model to the experimental data, reliable quantitative information on the orientational properties of the C-Br bonds is determined. The experimental strategy reported here represents the basis of a new approach for gaining insights into the orientational properties of molecules in anisotropic materials.

Chirality, birefringence, and polarization effects inα-quartzstudied by resonant elastic x-ray scattering

“…The effect of small variations of the polarization characteristics has already been reported by Palmer et al [15]. Measuring the linear component of the polarization light is rather common, but the precise access to the full polarization state is not easy [16].…”

Developments in Structural Chemistry from the Viewpoint of a Solid‐state Chemist: A Review Prompted by the Sixtieth Anniversary of Professor Jack Dunitz's Research Group in the ETH, Zurich

“…The phenomenon of X‐ray birefringence was demonstrated only recently,, initially using a narrowly focused X‐ray beam that did not provide spatially resolved mapping of the material. Subsequently, an experimental setup (Figure ) was developed to allow spatially resolved measurements of X‐ray birefringence to be carried out in an imaging mode, using a large‐area linearly polarized incident X‐ray beam and an area detector .…”

Novel technique for spatially resolved imaging of molecular bond orientations using x-ray birefringence

“…Recently, crystals of certain compounds have been found to show birefringence of Xrays tuned to an absorption edge of one of the types of atom present in the material [1,2]. While optical birefringence arises from the global anisotropy of the crystal, X-ray birefringence arises from the locally anisotropic environment of the selected type of atom, and may therefore be used to study the orientational properties of molecules and bonds.…”