|VIPER (Visual Processing in EXAFS Researches)
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Several glitch corrections on absorptance curve with simultaneous
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
Given XPS-spectrum (measured or calculated) near and deeper than the
edge, one can extract a one-electron absorption from the total one (by
means of Bayesian
deconvolution procedure) and use then a quite clear one-electron theory
An EXAFS-part, chi(k), extraction. Three methods for construction of the
are realized: (i) by a spline drawn through the knots varied to minimize
low-r 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 atomic-like absorption (edge
multi-electron contribution, etc.). chi(k) extraction can be verified
Fourier-transform and back Fourier-transform. 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, k-weighting, several windowing functions. Phase
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 multiple-scattering contributions:
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 r-space.
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
chi^2- and F- tests can be performed at user request.
By ordinary EXAFS formula.
Using the oscillatory potential U(r) of the absorber-scatterer 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.
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.