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XAS Tutorials XAS Data Exchange (Converting PROCESS *.frm to Artemis *.chi) (You must first install ifeffit) Athena is the GUI for ifeffit that handles data processing and reduction. However, in our group, it is more common to use EXAFSPAK to do the data reduction, resulting in a *.frm ASCII file containing two columns (k, chi). These EXAFS data can be imported directly into Artemis, but because of some compatibility issues, it is best to import them into Athena and then use Athena to export the input file for Artemis. For this tutorial, a number of example files are contained in a zip archive called ifeffit_tutorial_a. You should download and unpack this archive now and leave the folder in an accessible place. In this folder is a file called zrdwa.frm that contains Zn EXAFS data for [Zn]rubredoxin, which we will use as an example. First, start up Athena and from the GUI, use the File menu to select Open file. Find zrdwa.frm and select it. These EXAFS .FRM files are also often named xxxxx-k3x.frm in which there are three columns of data [k, chi(k), k3*chi(k)]. The following shows what happens when there are three columns, although zrdwa.frm has only two:
You should see two more windows appear: one is a Graphics Window and the other is a data columns window. You need to select which column should be in the Numerator; pick column 2 (chi). Your data will then appear in the Graphics Window. Then you should select chi(k) from the Data type dropdown menu. Then click OK.
The Graphics Window should change the display to k*chi vs. k. When you export from Athena, the file will have a header, so you might as well set some of these parameters here. For example, set the atomic number (Z) and Edge to Zn and K (for this example).
This is all you need Athena for, so now export these data by choosing Save chi(k) from the File menu. Choose the filename zrdwa.chi and save it in the folder where you found zrdwa.frm. (If it already exists, you can replace it.) You can quit Athena; no need to save the project. You are now ready to start using Artemis for curve-fitting. scott@chem.uga.edu |
