Re: [Ifeffit] Bug in Athena?

Hi Matt, I'm the one who requested the merged reference channel. If the data is ideal, of course only one reference scan is needed. But there are two common ways it can be nonideal that are relevant: 1) The monochromator does not hold calibration; i.e. there is an energy shift between scans 2) The reference channel is very noisy, perhaps because of an inherently thick sample If 1) is a significant problem and 2) is not, then it makes sense to align the scans using the reference, at which point any reference scan will do for determination of the chemical shift of the merged data from the sample. If 2) is a significant problem and 1) is not, then it makes sense to merge the references along with the sample data, because that will make it easier to determine the chemical shift. If both problems are significant, then you've got a headache. --Scott Calvin Sarah Lawrence College On Nov 19, 2009, at 10:26 AM, Carlo Segre wrote:

Hi Matt:

I agree. It is useful to have the reference channel from the first of the merged data pulled over as reference for the merged data but this actuallly only makes sense if the user first aligned using the reference.

carlo

On Thu, 19 Nov 2009, Matt Newville wrote:

...

Is there ever a case where a merged reference channel is useful?

I thought the only possible use for a reference channel was for comparing individual scans. That is, prior to merging.

--Matt

On Thu, Nov 19, 2009 at 6:45 AM, Zajac, Dariusz A. wrote:

...

Dear Bruce, Dear All, maybe it is a naïve question but I want to ask and to point this problem...

Windows XP. Athena 0.8.059 Sc.Linux. Athena 0.8.060

I have a set of data with refernces (one sample, many scans). I have marked sample's groups and do "merge marked data in mu(E)" then I get merged data together with reference (2 groups: merge - sample, and Ref merge - reference). But... ...if I have marked reference sample's groups and do "merge" then I get 2 groups: merge - which is merged data of reference, and Ref merge - which is marged data of sample. Oposite to that I did in first example!

Is any hidden idea, I can not see, why it should be that way? If you don't know about that, can confuse and surprise... cheers darek _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit

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-- Carlo U. Segre -- Professor of Physics Associate Dean for Graduate Admissions, Graduate College Illinois Institute of Technology Voice: 312.567.3498 Fax: 312.567.3494 segre@iit.edu http://www.iit.edu/~segre segre@debian.org_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit