Hi, I compared the background subtracted data of my code with the data I got with Athena and with my code the data always looked as if the spline clamps did not work, since the chi(k) curve was diverging at the border at high k-values... However since you said the syntax is correct I tried it again today with a new script and now it works fine so probably there was some other stupid error. So sorry for bothering you and thanks for the answer which was very helpful :), Jan Zitat von Bruce Ravel :

On Monday 07 December 2009 05:37:41 am you wrote:

...

Hi Bruce,

I have a question concerning the spline clamps in ifeffit. Is there any possibility to set them directly in the spline() command? I tried to do it with spline(..., clamp1=0, clamp2=24,...) but it did not work and by default both spline clamps seem to be zero. Unfortunately I found nothing about it in the reference guide either. So how can I configure the clamps in the Ifeffit code?

Thanks and kind regards,

Hi Jan,

I am CCing this to the Ifeffit mailing list, which is the better place to ask a question of this sort. I was out of town all of last week -- had you sent this to the mailing list rather than to me directly, you probably would already have received an answer.

You seem to have the syntax correct. That is, if you follow along in Athena's Ifeffit buffer, you see that "spline(..., clamp1=0, clamp2=24,...)" is exactly what she does. Anything you see in the Ifeffit buffer should be directly transplantable to an Ifeffit script. Indeed, that is the very purpose of making the Ifeffit buffer available to the user.

So, what do you mean that the clamps both seem to be zero? How do you know that? Can you show us an example data file and a short example ifeffit script that demonstrates the problem? It is quite possible that changing the clamp strength will have no significant impact of the background removal. To refresh my memory as I am writing this email, I loaded an iron foil spectrum into Athena. Indeed, changing clamp 2 has little impact on the background removal. But I know from experience that, in general, it does.

Just to tell the whole story, I'll point out that the numeric values of the clamp strengths in Athena are configurable. If you go to Edit preferences, then open the clamp group, you will be able to assign new values to the 5 named clamp strengths.

HTH, B

--

Bruce Ravel ------------------------------------ bravel@bnl.gov

National Institute of Standards and Technology Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2 Building 535A Upton NY, 11973

My homepage: http://xafs.org/BruceRavel EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/

-- Dipl.-Phys. Jan Stötzel Fachbereich C / Physik, Bergische Universität Wuppertal Gaußstr. 20, D-42097 Wuppertal, Germany E-mail: j.stoetzel@uni-wuppertal.de phone: +49 202 439-3105, fax: -3101, secretary: -3102 http://hydrogen.physik.uni-wuppertal.de/index.html