Hi Maria Automatic Divergence Slits (ADS) illuminate different parts of the post monochromator as a function of 2Th. I am guessing but I think that the crystals are good enough not to change the intensity too much; this is my experience with Y2O23 in any case.
At around 70 to 80 degrees 2Th however the beam (typically around 4 degrees in the equatorial plane) spills out of the post monochromator. This situation should be avoided; instead above that angle the slits should be fixed. Thus you have the situation where part of your pattern is analysed using ADS corrections and part using FDS corrections. ADS corrections comprise: - A Sin(Th) scaling of intensities - A change in peak shape Note, that anti scatter slits could also influence intensities at large divergences. Cheers Alan -----Original Message----- From: Fabra-Puchol, Maria [mailto:[EMAIL PROTECTED] Sent: Tuesday, 27 March 2007 12:03 AM To: rietveld_l@ill.fr Subject: Use fix or programmable slits for Rietveld analysis Hi all, I have a question using fix (FDS) and programmable slits (ADS) for Rietveld analysis. Actually, I work with a X'PERT equipment with fast detection and with programmable divergence slits in the incident beam and a programmable antiscattering slits in the diffracted beam. I have also the possibility to use them in a fix mode. I would like to know the opinion of the community about the best configuration of this slits (fix or programmable) if a Rietveld analysis is required. In fact, using programmable slits, the software corrects data and changes from ADS to FDS. What is the interest to use ADS in this case? Thank you all Maria Fabra Puchol Microanalysis Engineer Saint-Gobain CREE --------------------------------------- 550, Avenue Alphonse Jauffret 84306 Cavaillon Cedex-France [EMAIL PROTECTED] telf: +33 (0)4 32 50 09 36 fax: +33 (0)4 32 50 08 51
