
VIPER (Visual Processing in EXAFS Researches) 

HARDWARE  
Windows

DOWNLOAD  
Download the latest version here

AUTHORS  

K.V.Klementev

NOTES  

Several glitch corrections on absorptance curve with simultaneous
observation of
the EXAFS curve. Before this, glitches are detected on the derivative
level of the
first ionization chamber current.

Deconvolution of absorption coefficient with monochromator resolution
curve.

Given XPSspectrum (measured or calculated) near and deeper than the
chosen absorption
edge, one can extract a oneelectron absorption from the total one (by
means of Bayesian
deconvolution procedure) and use then a quite clear oneelectron theory
without complicated
manybody corrections.

An EXAFSpart, chi(k), extraction. Three methods for construction of the
atomiclike absorption
are realized: (i) by a spline drawn through the knots varied to minimize
lowr EXAFS part;
(ii) by a smoothing spline and (iii) by a Bayesian smoothing curve. The
last two can take
into account a priori information about atomiclike absorption (edge
shape, AXAFS,
multielectron contribution, etc.). chi(k) extraction can be verified
simultaneously by
Fouriertransform and back Fouriertransform. chi(k) or chi(E) can be
corrected by arbitrary
functions f(k) or f(E). Errors of chi(k) are calculated by various ways
in order to validate
the spectrum extension.


Fast Fourier analysis, kweighting, several windowing functions. Phase
and amplitude
corrections. Decomposition into amplitude and phase and subsequent
calculation of the EXAFS
amplitude and phase.

Fitting procedures for the first few coordination shells not influenced
by the multiplescattering contributions:

By ordinary EXAFS formula.

Using the oscillatory potential U(r) of the absorberscatterer pair. The
potential U(r) is set
by typed in arbitrary formula, parameters of which then are varied. U(r)
may consist of many
wells. Both classical and quantum approaches are used.

All fit parameters can be fixed and constrained or related to the
homogeneous parameters of the
other spheres (wells) by arbitrary functions. Fitting is done either in
k or in rspace.
Scattering amplitudes and phases must be calculated by other programs
(FEFF format is
recognized). The parameters and results of fitting can be saved in (and
then a model can be
loaded from) a database. Advanced error analysis is developed and
applied. Statistical
chi^2 and F tests can be performed at user request.

Any time, all curves and their changes under processing are visual.
Several parameters can be
quickly changed by mouse dragging.

Data file structure is tunable and flexible, no previous conversion
needed to load multiple
column files from different EXAFS stations.

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