[Ifeffit] Bug in Athena?

[Scott Calvin]

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.
>> <dariusz.zajac at desy.de> 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 at millenia.cars.aps.anl.gov
>>> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>>>
>>>
>> _______________________________________________
>> Ifeffit mailing list
>> Ifeffit at millenia.cars.aps.anl.gov
>> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>>
>
> -- 
> 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 at iit.edu   http://www.iit.edu/~segre   segre at debian.org_______________________________________________
> Ifeffit mailing list
> Ifeffit at millenia.cars.aps.anl.gov
> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit