Uncertainty can get fairly close to 0 (+/- 0.1) but amp gets up anywhere from 2 to 4 depending on what data set I'm fitting to. ----- Original Message ----- From: "Scott Calvin" To: "XAFS Analysis using Ifeffit" Cc: Sent: Monday, February 27, 2006 10:56 AM Subject: Re: [Ifeffit] Amplitude in Artemis

How far above 1? And with what uncertainty?

--Scott Calvin Sarah Lawrence College

At 07:52 PM 2/26/2006, you wrote:

...

I have just started a PhD and have been given alot of EXAFS data to simulate but I don't know much about artemis. I have tried to fit the data for quite some time now, but can't get any kind of good fit unless the amplitude is above 1. Is there any way amp can be above 1 and rationally explained?

_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit

Pre and post edges are fine, and the model I'm using is made from the crystallographic data collected. I wouldn't have thought getting a decent fit with good data is difficult with the crystal structure as the model. But I'm assuming there is not any kind of reason amp can be above 1. Problem is, if I restrain it to be between 0 and 1 it sits at 1 with an error of +/- 40. ----- Original Message ----- From: "Scott Calvin" To: "XAFS Analysis using Ifeffit" Sent: Monday, February 27, 2006 11:19 AM Subject: Re: [Ifeffit] Amplitude in Artemis

Hi Paul,

The most likely possibilities are:

1) The normalization (in Athena or whatever) is way off. Make sure you check it by eye and see that the pre-edge or post-edge line isn't crazy for some reason.

2) The model isn't right...your samples are not what you think they are.

So no, I don't think you have a legitimate fit at this point.

--Scott Calvin Sarah Lawrence College

At 08:11 PM 2/26/2006, you wrote:

...

Uncertainty can get fairly close to 0 (+/- 0.1) but amp gets up anywhere from 2 to 4 depending on what data set I'm fitting to.

_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit