[Ifeffit] Too many points in pre-edge

[Carlo U. Segre]

On Thu, 2 Dec 2004, Bruce Ravel wrote:

> On Thursday 02 December 2004 04:40 pm, Matt Newville wrote:
>
>> It's quite possible that it would miss e0 in data with an
>> unexpectedly long pre-edge.
>
> I can see the argument that ifeffit should have been able to figure
> this out, but it does seem kind of silly to bin the data in the
> pre-edge such that the energy steps are about 1/2 volt.  That vastly
> overspecifies the pre-edge.
>

As I mentioned earlier, these data are taken in continuous scan mode. 
The monochromator is set to run at a constant speed and data is taken on a 
constant time interval basis with a multichannel scaler.  This results in 
a high point density over the entire range.  We sum spectra and rebin in 
the EXAFS region so that we can keep all the statistics possible (we had 
an extensive discussion of this on this list about a year ago).  However, 
it is of use not to reduce the point density of the edge so we just don't 
rebin before the edge.  Since the pre-edge is normally flat, we chose not 
to alter it at all.  This results in the problem that we are discussing. 
I think that we might as well change our program to rebin the pre-edge as 
well and this will solve the problem

Carlo

-- 
Carlo U. Segre -- Professor of Physics
Associate Dean for Special Projects, Graduate College
Illinois Institute of Technology
Voice: 312.567.3498            Fax: 312.567.3494
Carlo.Segre at iit.edu    http://www.iit.edu/~segre