Matt >I am not sure I understand how you would account for the additional >wavelengths in the beam.
Tube tails is spectrally independent and its aberration shape is 2Th independent. Its realized in TOPAS by a convolution called stacked_hats which, as its name suggests, convolutes a series of stacked impulse functions. An intense narrow hat represents the beam and wider hats the penetration of the electrons in the tube. Cheers Alan -----Original Message----- From: Matt Beekman [mailto:matt.beek...@oit.edu] Sent: Tuesday, 17 September 2013 2:08 AM To: Peter Y. Zavalij; Alan Coelho; mariomac...@tux.uis.edu.co; rietveld_l@ill.fr Subject: RE: Instrumental resolution function Alan, Peter, Would you mind briefly elaborating on the procedure used to "fit tube tails?" I personally have only used GSAS for Rietveld refinement, and other than adding another phase(s) with slightly different lattice parameter(s) I am not sure I understand how you would account for the additional wavelengths in the beam. Many thanks in advance! Matt -- Matt Beekman, Ph.D. Assistant Professor of Physics Department of Natural Sciences Oregon Institute of Technology 3201 Campus Drive Klamath Falls, OR 97601 Tel: 541-885-1940 Fax: 541-885-1849 Email: matt.beek...@oit.edu Web: http://www.oit.edu/faculty-staff/home-pages/natural-science/matt-beekman -----Original Message----- From: rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] On Behalf Of Peter Y. Zavalij Sent: Monday, September 16, 2013 6:11 AM To: Alan Coelho; mariomac...@tux.uis.edu.co; rietveld_l@ill.fr Subject: RE: Instrumental resolution function I do exactly the same - fit tube tails using LaB6 standard and use the parameters (usually w/o fitting) in all other refinements. Although tube tails fitting helps a lot it's not perfect. Peter Zavalij -----Original Message----- From: Alan Coelho [mailto:alancoe...@bigpond.com] Sent: Sunday, September 15, 2013 10:05 PM To: Peter Y. Zavalij; mariomac...@tux.uis.edu.co; rietveld_l@ill.fr Subject: RE: Instrumental resolution function Hi Peter, Mario I happen to have a Ni filter, Cu, LaB6 pattern that has a very similar look to the one sent by Mario. Probably best to look at the 21.35 degrees 2Th peak. The Ni filter cut-off occurs at 20.6 degrees 2Th, the satellite group is hard to see due to the low angle and hence compression of the emission profile. What made sense in the pattern was to fit Tube tails. Across the whole patter the Rwp was reduced by 2.1% where Tube tails was considered and the fit at the shoulders was good. Cheers Alan -----Original Message----- From: rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] On Behalf Of Peter Y. Zavalij Sent: Monday, 16 September 2013 10:55 AM To: mariomac...@tux.uis.edu.co; rietveld_l@ill.fr Subject: RE: Instrumental resolution function Hi Mario, The shoulder you observe is what's left from "white" after it is cut off by beta-filer. You could check the absorption edge of Ni and it is right at the shoulder you observe. Peter __________________________________ Peter Zavalij X-ray Crystallographic Center University of Maryland College Park, MD 20742 Phone/Fax: (301)405-1861 http:/www.chem.umd.edu/crystallography -----Original Message----- From: rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] On Behalf Of mariomac...@tux.uis.edu.co Sent: Sunday, September 15, 2013 6:08 PM To: rietveld_l@ill.fr Subject: Instrumental resolution function Dear All, I am calculating the corresponding instrumental resolution function of our Bruker diffractometer which is operating in Bragg-Brentano geometry with Cu radiation, using a nickel filter and LynxEye detector. The calculation is carried out by the Rietveld analysis of the LaB6 (660b) NIST-standard. We observed the Kbeta peaks, but also some shoulders in the left part of the peaks. We have some ideas about this but taking into account that I'm not an actual expert, your comments will be very important to me. In the attached file, I send an image to make a better illustration of my doubts. Thanks in advance for your help. Best Regards, Mario A. Macías Universidad Industrial de Santander Bucaramanga-Colombia.
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