Design of a Solid Inclusion Compound with Optimal Properties as a Linear Dichroic Filter for X‐ray Polarization Analysis

Abstract

Mithilfe theoretischer Vorhersagen der erforderlichen Struktureigenschaften wurde die Einschlussverbindung von 1‐Bromadamantan mit Thioharnstoff (siehe Bild) als dichroitischer Filter für die Polarisationsanalyse von Röntgen‐Strahlung entwickelt. Der lineare Dichroismus, den die Substanz mit Röntgen‐Strahlung zeigt, bestätigt ihre optimale Eignung für die gewünschten Anwendungen.

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

“…Indeed, the first definitive demonstration of X-ray birefringence was only reported very recently and focused on a model material that was shown to exhibit essentially ideal birefringence behavior at X-ray energies near the Br K-edge. The designed material (the 1-bromoadamantane/thiourea inclusion compound) gave experimental behavior in excellent agreement with theoretical predictions for the dependence of transmitted X-ray intensity on both X-ray energy and crystal orientation for the case of a material in which all C–Br bonds are aligned strictly parallel to each other and with a known orientation of the C–Br bonds relative to the crystal axes. However, given the strong interdependence between X-ray birefringence and the orientational characteristics of specific bonds in materials, there is considerable potential to exploit measurements of X-ray birefringence to establish insights into bond orientational properties for cases in which the bond orientations are unknown or poorly characterized (e.g., in the case of disordered materials).…”

X-ray Birefringence from a Model Anisotropic Crystal

“…The interaction of linearly polarized visible light with solids is well understood, including the phenomena of dichroism and birefringence, for which absorption (in the case of dichroism) and refractive index (in the case of birefringence) depend on the orientation of an anisotropic material with respect to the plane of polarization of the incident radiation. While widely studied for visible light, these phenomena are far less established for linearly polarized X-rays, although we note that research on X-ray dichroism − has included recent studies of dichroic filter materials for applications in magnetic X-ray scattering and X-ray astronomy . In the present Letter, we report the first definitive demonstration of X-ray birefringence, reporting a material that exhibits essentially ideal birefringence behavior at X-ray energies near the Br K-edge.…”

“…Therefore, materials that exhibit linear dichroism generally also exhibit birefringence, and these phenomena depend on the same structural (and symmetry) properties of the material. Given our previous development of materials that exhibit significant X-ray dichroism, − we were motivated to explore the possibility that such materials may also exhibit X-ray birefringence. Surprisingly, very few experimental studies of X-ray birefringence have been reported, − and significantly, all previous studies involved complex experimental setups, typically with the detection of extremely weak signals.…”

“…The successful development − of X-ray dichroic filter materials suitable for operating at X-ray energies near the Br K-edge was based on urea and thiourea inclusion compounds, − which comprise guest molecules of suitable size and shape spatially confined within a host tunnel structure constructed from the urea or thiourea molecules. The key advantage of exploiting such solid inclusion compounds in the development of materials for applications based on X-ray dichroism (and here X-ray birefringence) devolves upon the fact that the host structure exerts a very strong orienting influence on the guest molecules, and thus with appropriate choice of both the host structure and the guest molecules, materials can be designed in which the orientations of specific bonds of the guest molecules (in the present case, C–Br bonds) can be exquisitely controlled.…”

Theoretical analysis of the background intensity distribution in X-ray Birefringence Imaging using synchrotron bending-magnet radiation

“…In order to show the effectiveness of the X-ray Birefringence Imaging method, the bright trace left by a birefringent sample is also labelled in Figure 7. The specific samples are a single crystal of the 1-bromoadamantane/thiourea inclusion compound (Chao et al, 2003) at 280 K in the case of the Si (5 5 5) analyzer ( Figure 7(a); data from Palmer et al (2014)) and a single crystal of the 1,8-dibromooctane/urea inclusion compound (Harris et al, 1991;Guillaume et al, 1994) at 100 K in the case of the Ge (5 5 5) analyzer ( Figure 7(b); data from Palmer et al (2015)). The X-ray optic axis of the sample is oriented by the diffractometer to an angle of þ45 (Figure 7(a)) and þ44 (Figure 7(b)) with respect to the horizontalẑ-axis of Figure 4.…”