[Ifeffit] EXAFS mean free path in small particles

John J. Rehr jjr at leonardo.phys.washington.edu
Mon Jun 20 12:11:04 CDT 2005

Hi Matt,

  Thanks for the interesting Cu fits.

  Clearly the coorrelations between S02, ThetaD and Ei make any
assessment of possible problems with Ei problematic. Also, I don't
know what the experimental resolution Gamma_expt is - probably some
fraction of an eV, so Ei=Gamma_expt+Im delta Sigma implies a comparable 
but negative correction delta Sigma  to the self-energy, which is
evidence of excessive loss in the HL plasmon-pole self-energy for Cu.

   Moreover,  although your fits are in R-space, inspection of the k-space data
shows that contributions from distant MS paths are suppressed by the theory,
also suggesting that FEFF's PP self-energy overestimates loss.

   It will be interesting to see what Ei does if one forces S02=0.9
(based on Luke Campbell's theoretical estimate) and ThetaD=315 K.
We'll also try to make an independent fit using the Bayesian/EXAFS+XANES
scheme that we're working on here.

   J. Rehr

> |-----------------------------------------------------------------|
> |Fit  S02       ThetaD    Ei        E0        dR       chi_reduced|
> |-----------------------------------------------------------------|
> |#1  0.93(0.03) 271(12)  0.0( - ) 0.7(0.4) -0.003(0.002)  12.8    |
> |#2  0.78(0.09) 300(23) -1.5(0.9) 0.7(0.3) -0.003(0.001)  10.9    |
> |-----------------------------------------------------------------|

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