The correction of reflection intensities for incomplete absorption of high-energy X-rays in the CCD phosphor

• Published in: Journal of applied crystallography Vol. 35; no. 3; pp. 356 - 359
• Main Authors: Wu, G., Rodrigues, B. L., Coppens, P.
• Format: Journal Article
• Language: English
• Published: 5 Abbey Square, Chester, Cheshire CH1 2HU, England Munksgaard International Publishers 01.06.2002; Blackwell
• Subjects: ABSORPTION; area detector; ATOMIC DISPLACEMENTS; CCD phosphor; CHARGE DENSITY; Condensed matter: structure, mechanical and thermal properties; DEFORMATION; Exact sciences and technology; high-energy synchrotron radiation; MULTIPOLES; oblique correction; PARTICLE ACCELERATORS; PHOSPHORS; Physics; REFLECTION; Single-crystal and powder diffraction; Structure of solids and liquids; crystallography; SYNCHROTRON RADIATION; WAVELENGTHS; X-ray diffraction and scattering; Charge coupled devices; Absorption correction; Bias; Oblique incidence; Structure resolution; Refinement; Electron charge distribution; XRD; X-ray absorption; Phosphors; Incidence angle; Error correction; Synchrotron radiation; Crystal structure
• ISSN: 1600-5767; 0021-8898; 1600-5767
• DOI: 10.1107/S0021889802005770

It is shown that incomplete absorption of the X‐ray beam in the phosphor of an area detector causes an incident‐angle dependence of the recorded X‐ray intensities. An energy scan of a SMART‐6000 CCD (charge‐coupled device) phosphor using synchrotron radiation shows the correction to be of importance above about 17 keV. Intensities of single reflections, each collected several times at different angles of incidence on the phosphor surface, show a pronounced angle‐dependence at shorter wavelengths. Both conventional structural refinement and multipole charge density studies confirm that an oblique‐incidence correction leads to improved quality of the results. Atomic displacement parameters will be systematically biased when the correction is not applied. For a λ = 0.394 Å data set, neglecting the correction gives rise to artifacts in the deformation density maps that are likely to lead to misinterpretation of the experimental results.