Compute X-ray Absorption

Select X-ray Wavelength or Energy: (click for details)
Select Wavelength or Energy from the pull-down menu
Enter valid X-ray wavelength (or energy) in the range 0.05 - 3.0 Å (248 - 4.13keV)
Valid range is reduced for high Z elements (Z > 78), see 'more information' in About section below for details
Wavelength (Å) Energy (keV)

Chemical Formula: (click for details)
Accepts all elemental symbols in the range H (Z=1) to Cf (Z=98)
Note: absorption for H and He is assumed zero and not included in calculation
Fractional formula unit occupancies are rounded to the nearest hundredth (0.01)
Entered formula (assuming unit cell Z = 1) is used to estimate sample density if "packed faction" is selected below

enter using element chemical symbol and formula unit occupancy, e.g. YBa2Cu3O6.5 (proper capitalization is required)

Sample Radius: (click for details)
Enter radius (in millimeters) of capillary used for transmission geometry (Debye-Scherrer) powder X-ray diffraction measurement
capillary radius in mm

Sample Density or Packing Fraction (click for details)
Select 'Sample Density' or 'Packing Fraction' from the pull-down menu
'Sample Density' is more accurate, however 'Packing Fraction' provides a good estimate if real packed sample density is not known.
'Sample Density' refers to the actual measured density (in g/cc) of a capillary sample loaded with powder
'Packing Fraction' refers to the estimated packing fraction of sample powder in the capillary (often ~ 0.6)
When 'Packing Fraction' is selected, the sample density is estimated assuming 10 cubic Å per atom in the entered chemical formula
The accuracy of this estimate is typically good to ± ≈ 25% of experimental density

enter measured sample density or estimated packing fraction (often ~0.6)

Sample Density (g/cc) Packed Fraction (0.0 - 1.0)

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About: This routine estimates capillary sample absorption for transmission geometry (Debye-Scherrer) powder X-ray diffraction measurements.
(click here for more information) Capillary sample absorption is estimated (based on user supplied data and calculated f' & f" values) for elements between Li - Cf and in the X-ray wavelength range 0.05 - 3.0Å (248-4.13keV) using the Cromer & Liberman algorithm (reference: Acta Cryst. 1981 v.A37, p.267) and orbital cross-section tables. Note that the Cromer - Liberman algorithm fails in computing f' for wavelengths < 0.16 Å (> 77.48 keV) for the heaviest elements (Au-Cf) and fails to correctly compute f', f" and mu for wavelengths > 2.67 Å (< 4.64 keV) for very heavy elements (Am-Cf).

Web utility created by Robert B. Von Dreele, Matthew R. Suchomel and Brian H. Toby, based on the python software package Absorb (download here).

» Return to 11-BM X-ray absorption webpage

New feature: define your own custom absorb.php bookmark with default wavelength settings (or sample radius etc)

Example: try the URL http://11bm.xray.aps.anl.gov/absorb/absorb.php?spectrum=1.54&radius=0.5&density=1.0

Last Modified: Feb 2013