[Ifeffit] Re: from I.Demchenko ...

[Matt Newville]

Bruce, Iraida, 

> On Tuesday 06 April 2004 12:12 pm, Iraida Demchenko wrote:
> > I have a problem with fitting of my data for 0.5 microns  of Ge on
> > Si(001) substrate (grown by MBE). The spectrum for K-edge of Ge was
> > collected by TY mode. This sample is a standard for my next
> > fitting. >From this fitting (for 1 shell)Â I want to draw
> > So^2... But, if I apply a "trick" with k-weight determination as 1
> > and So^2 value changing from 0.7 to 1.1 and repetition of this
> > operation for k^1, k^2, k^3, I get three parallel lines for
> > sigma^2(Ge-Ge) as function of So^2 :(. They aren't crossed in this
> > area.
> 
> This is kind of surprising to me.  I have used the three-lines trick
> many times and have never seen the situation of three parallel lines.
> I am a little confused how that is even possible.  One might expect
> this trick to do strange things in the case of a first shell that is
> not well separated from higher shells, but my memory of Ge is that the
> first shell is well separated.

What is the "three-lines trick"?  It sounds like Iraida ran several
different fits with kweight of 1, 2, or 3, stepping through set
values for S02 ranging between 0.7 and 1.1, and fitted sigma2 (and
possibly other parameters???).  Is that right?  

Sorry to be so dense, but what lines are supposed to cross and what
is this supposed to tell you?

--Matt