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

Sutter, John P., Dolbnya, Igor P., Collins, Stephen P., Harris, Kenneth David Maclean, Edwards-Gau, Gregory R., Kariuki, Benson and Palmer, Benjamin A. 2016. Novel technique for spatially resolved imaging of molecular bond orientations using x-ray birefringence. Presented at: 12th Annual Conference on Synchrotron Radiation Instrumentation - SRI2015, New York City, NY, USA, 6-10 July 2015. Proceedings of the 12th Annual Conference on Synchrotron Radiation Instrumentation - SRI2015. American Institute of Physics, 050009. 10.1063/1.4952929

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Abstract

Birefringence has been observed in anisotropic materials transmitting linearly polarized X-ray beams tuned close to an absorption edge of a specific element in the material. Synchrotron bending magnets provide X-ray beams of sufficiently high brightness and cross section for spatially resolved measurements of birefringence. The recently developed X-ray Birefringence Imaging (XBI) technique has been successfully applied for the first time using the versatile test beamline B16 at Diamond Light Source. Orientational distributions of the C–Br bonds of brominated “guest” molecules within crystalline “host” tunnel structures (in thiourea or urea inclusion compounds) have been studied using linearly polarized incident X-rays near the Br K-edge. Imaging of domain structures, changes in C–Br bond orientations associated with order-disorder phase transitions, and the effects of dynamic averaging of C–Br bond orientations have been demonstrated. The XBI setup uses a vertically deflecting high-resolution double-crystal monochromator upstream from the sample and a horizontally deflecting single-crystal polarization analyzer downstream, with a Bragg angle as close as possible to 45°. In this way, the ellipticity and rotation angle of the polarization of the beam transmitted through the sample is measured as in polarizing optical microscopy. The theoretical instrumental background calculated from the elliptical polarization of the bending-magnet X-rays, the imperfect polarization discrimination of the analyzer, and the correlation between vertical position and photon energy introduced by the monochromator agrees well with experimental observations. The background is calculated analytically because the region of X-ray phase space selected by this setup is sampled inefficiently by standard methods.

Item Type: Conference or Workshop Item (Paper)
Date Type: Publication
Status: Published
Schools: Chemistry
Subjects: Q Science > QD Chemistry
Publisher: American Institute of Physics
ISBN: 9780735413986
ISSN: 0094-243X
Date of First Compliant Deposit: 14 October 2016
Last Modified: 28 Jun 2019 14:40
URI: http://orca-mwe.cf.ac.uk/id/eprint/94510

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