[Ifeffit] Fit XANES spectra using Athena

[Adam Webb]

Hi Jenny,

I don't know what exactly you are trying to do so I can't say which
method is better but I can make a comment.

It all comes down to the number of independent variables. The Gaussian
and step functions are independent of each other. The heights, widths
and positions can all be adjusted. In the linear combination you change
everything together so for example, the ratio of the peak height and the
step height doesn't change. The result is that you need more spectra to
get the same number of degrees of freedom as in the least-squares peak fit.

Cheers,
Adam

Jenny Cai wrote:
> Hello everyone,
> 
> Sorry for bothering you again.
> 
> I am using least-squares peak fit and linear combination fit to analyze
> my samples. I have spent tons of time on it, and it really makes me
> crazy. Why can't I get consistent results from these two methods?
> 
> Please see the attached file. Both of these methods work well
> individually, but linear combination fit always need more peaks than
> peak fit to get an 'ok' fitting. Should I stick on one method for all my
> samples, no matter what results the other one gives? It is confusing me
> so much. Could anyone help me out?
> 
> Thank you in advance for your help!
> 
> 
> Jenny
> 
>