Dear João

I have read J. I. Langford's article (J. Appl. Cryst. 2000. 33, 964-974 ) and 
there I saw the following  equation for the line profile (that was obtained 
from A.J.C. Wilson-1962):
I(2theta) = [cos(theta)/lambda] I(s)
I would like to know what the exact  meaning of the cos(theta) factor in this 
equation is. What does it describe?
I will be very grateful for some help.

the term just account for the passage (done in the formula) from reciprocal space to 2theta space. Easy to demonstrate:
 s = 2 Sin[theta]/lambda
so, taking the differential (for fixed lambda)
 ds = 2 Cos[theta]/lambda dtheta = Cos[theta]/lambda d(2theta)
Enjoy

M

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 Matteo Leoni, PhD

 Department of Materials Engineering
 and Industrial Technologies
 University of Trento
 38050 Mesiano (TN)
 Italy

 Tel +39 0461 882416    e-mail:        [EMAIL PROTECTED]
 Fax +39 0461 881977    Web:    www.matteoleoni.ing.unitn.it

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