[Ifeffit] Using more than one E0

[Matt Newville]

Hi Scott,

Oh, I definitely agree that C3 can be important, even below 
room temp for some systems.  The questions are (or were) if 
using more than one E0 is ever needed and whether it can be 
justified.  It seems to me that the answer to that is yes.

You suggested that multiple E0s might be a manifestation of 
needing a C3 but instead compensating with an additional E0 
as a fudge factor.  It should be easy to make up some data 
with a non-zero C3 and try to fit it with multiple E0s, or 
to make up data with multiple E0 shifts and see how well it 
could be fit with a C3.  That might be a fun little project 
for a student.  If someone were to try this, I'd recommend 
adding some noise to the "data" using random(dist=normal).

--Matt