Diffuse scattering in benzil

Use of the RAPID II imaging plate system allows the collection of longer exposure images to enhance diffuse scattering without overloading pixels on the detector. Enhancing the diffuse scattering, however, also means enhancing the background, particularly in the form of air scattering and scattering from the beamstop. Therefore, it is useful to collect an empty instrument image and use this as a simple background correction by subtracting this from the observed image using AreaMax.

Benzil is an archetypal compound that is known to exhibit diffuse scattering, and has been well studied and modeled. The left image below shows a raw 30-minute exposure of benzil approximately aligned along the c-axis. Diffraction down this axis are dominated by broad "brick" shaped Bragg peaks and weaker hexagonal diffuse lines. It is possible to see some evidence of the weak hexagonal lines in the raw image but these are clearer in the corrected image (middle). However, the corrected image is quite pixilated, so multiple diffuse scattering images and background images were collected, merged and normalize to 30 minutes using AreaMax. Collecting multiple data images rather than one long image ensures that there is no risk of over-exposing the imaging plate with strong Bragg peaks.

The image at the right above shows is generated by merging six equivalent sample images (collected one after another), and corrected by six background images. The quality of the image is significantly enhanced with the hexagonal "bricks" being more apparent and the weak hexagonal lines becoming clear.

Results courtesy of Andy Parkin, Lynne H Thomas and Chick C Wilson, Structural Chemistry Group,  University of Glasgow

The D/MAX RAPID II is arguably the most versatile X-ray area detector in the history of materials analysis. In production for well over a decade and continuously improved during that time period, the success of the RAPID II is a testament to the suitability of imaging plate technology for measuring diffraction patterns and diffuse scattering from a wide range of materials. Read more...

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