[Ifeffit] delR and delE

Bruce Ravel ravel at phys.washington.edu
Thu Oct 14 13:23:49 CDT 2004


On Thursday 14 October 2004 2:02 pm, ritika.uppal at yale.edu wrote:
> I have another question. I have started from the beginning so that I
> could follow all of Shelly's suggestions. I also looked up your start
> guide for artemis fitting in which it says u can click the "fit
> background" button if u see low R peaks. And then in the end it says
> to click the "use previous background" button. but I can't seem to
> find it. Could anyone direct me??

That page is rather out of date.  The procedure for dealing with the
fitted background changed somewhat.  Here's the current situation:

1.  Co-refine the background by selecting the fit background button.
2.  Play around with the value of Rmin to get a good background
    co-refinement without undue correlations with the fitting
    parameters.  These correlations are reported in the log file.
    I would say that this procedure helps remove some of the mystery
    as the "correct" value for Rbkg -- the cutoff in Fourier space
    between background and data.  If the correlations are quite high,
    that value is probably too high since you may be damaging the data
    by allowing the spline too much freedom.
3.  In the Data menu is an option that says 'Save background
    subtracted as chi(k)'.  This will write a file containing the data
    with the fitted spline subtracted out to the project space.  You
    will then be offered an opportunity to replace the data with the
    background subtracted data.
4.  Choosing to import the background subtracted data will change the
    data and unselect the "fit background" button.
5.  You can now continue along with your data analysis, using the
    newly background-subtracted data.
6.  If you ever want to return to the non-background-subtracted data,
    select "Project data -> Import project data" from the File menu.
    This will open the file selection dialog in the folder where the
    project's data is stored.  You will see the original data along
    with the background-subtracted data and any other data you might
    have (at some point) imported into your project.

HTH,
B

-- 
 Bruce Ravel  ----------------------------------- ravel at phys.washington.edu
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