Absorption Correction Factors

Do you have any information about the use of the air absorption card in Denzo. The manual says that reflections are attenuated by e (2.78) but it says nothing about the angular dependence, or the wavelength dependence, both critical factors in determining the true effect of air absorption on reflection intensity.

The air absorbs equally in all directions! The program calculates air path and corrects for the absorption in the air. It is a very small correction.

Comment:  I think I've answered my own question about air absorption length appropriate for 0.9 A synchrotron radiation. It works out to 4500 mm using appendix 3 in Helliwell's book and the CRC Handbook of Chemistry & Physics.

Comment:  With regard to our discussion of air absorption, I looked up what is available in the International Tables and derived the equation log(mu) = 3.014*log(lambda) - 0.498 from some of the tabulated values. This gives the following values for input to Denzo:


air absorption length


590 mm


854 mm (Denzo default is 860)


928 mm


3145 mm