Absorption correction

Definition

Absorption correction is a method used in crystallography to adjust the measured intensities of diffracted X-rays to account for the absorption of X-rays by the crystal itself. This adjustment is critical because different parts of the crystal can absorb X-rays to varying extents, leading to inaccuracies in the collected data. Properly applying absorption correction ensures that the final data accurately reflects the true structure of the crystal, enhancing both data collection strategies and error analysis.

5 Must Know Facts For Your Next Test

1. Absorption correction is essential in single crystal X-ray diffraction to ensure accurate structure determination.
2. Different elements have different absorption coefficients, meaning that heavier atoms typically absorb X-rays more than lighter ones.
3. Absorption can vary within a crystal depending on its orientation relative to the incident X-ray beam.
4. Common methods for performing absorption corrections include analytical and numerical techniques, such as using the empirical absorption correction based on symmetry.
5. Failure to apply absorption corrections can lead to significant errors in derived structural parameters and hinder reliable interpretations of the crystal structure.

Review Questions

• How does absorption correction impact the quality of data collected in crystallography?
  • Absorption correction significantly impacts data quality by ensuring that intensity measurements accurately reflect the true scattering contribution from the crystal structure. If not corrected, variations in absorption across different parts of the crystal can distort intensity data, leading to inaccuracies in derived structural parameters. Thus, applying this correction is crucial for reliable analysis and interpretation of crystal structures.
• Discuss how different methods of absorption correction can affect precision and accuracy in crystallographic measurements.
  • Different methods of absorption correction, such as empirical versus theoretical approaches, can lead to varying levels of precision and accuracy. Empirical methods often use experimental data to refine corrections based on observed intensity variations, potentially yielding more accurate results. In contrast, theoretical methods might rely on model assumptions that may not capture all nuances of absorption behavior in complex structures, affecting overall measurement reliability.
• Evaluate the consequences of neglecting absorption correction when analyzing crystallographic data and its implications for structural determination.
  • Neglecting absorption correction can lead to severe consequences in crystallographic analysis, resulting in misrepresented structural information. It can cause systematic errors that skew intensity data, ultimately affecting bond lengths, angles, and electron density maps derived from this information. This oversight could lead to flawed interpretations of molecular arrangements and interactions, undermining the reliability of conclusions drawn from structural studies.

Related terms

Lorentz factor: A factor that accounts for the variation in intensity due to the geometric arrangement of the crystallographic planes during data collection.

Scattering factor: A measure of how much a particular atom scatters X-rays, which contributes to the observed intensity of diffracted beams.

Transmission: The fraction of X-rays that pass through a crystal without being absorbed or scattered, impacting the measured intensities.