DELIA (Dispersive Exafs caLIbration and Analysis)
Module characteristics
- Goal: To perform operations
over a bunch of spectra. Operations: calibration the spectra, extraction
of the XAFS signal and Fourier (and back-Fourier) filtering. This applications
has been designed for the particular needs of the ESRF/ID24 beamline. The Dispersive
XAFS and Turbo-XAS techniques generate a huge amount of XAFS spectra in
few seconds or minutes. This module allows the user to visualize the spectra,
calibrate them, extract the XAFS signal and perform Fourier and back-Fourier
transforms simultaneously over all the spectra by simply point-and-click.
- Input: a file with raw
data. Two possible ways of input data:
- CCD File
- ASCII: an ASCII file with a title, and an spectrum
per line, the first number is the index and then the channels. Example:
:log(I0/sample
0 -0.602633 -0.676992 -0.650588 ........... -0.686716 -0.650588
1 -1.287139 -1.292275 -1.289845 ............-1.287207 -1.286393
..............
1500 -0.504617 -0.503630 -0.503203.......-0.490741 -0.490417
- An ESRF Data
File with the spectral data.
- Sequential File:
- ASCII: a multicolumn file containing at least three
columns (more columns also accepted) with X,Mu
and index. The index
can be any value that identify the spectrum. Usually indices are 0,1,2...,
but can be, for example, a temperature value, etc.
- Binary: file that contains
three columns with X,Mu
and Index, all floats,
written in binary format by a big endian system. The file size is then
number_of_points*3*8
bits. Note that you can run DELIA in both little or big endian systems,
but the file must be written by a big endian system (or also by a little
endian system but swapping the byte ordering).
- Output: The results of
the operations performed with DELIA can be saved using the menu File->Export
CCD file. Note also
that many graphical applications used for visualization also allows writing
data in a number of different formats.
Example of use
The DELIA analysis is done in four main steps, Each step is implemented
in a different panel in the main window: Raw, mu(E), chi(k) and Fourier.
You should pass from one panel to the next one after completing the operations
in the current one. The names are self explanatory:
- Phase I [Raw]: allows to
read raw data, visualize the individual spectra, overplot them. You may
use the buton
for loading an example data.

You may export one of them for calibration.
- Phase II [mu(E)]: Interpolation
and Calibration. It allows the user to input the parameters. Default parameters
for the interpolation limits are presented. The minimum correspond to
maximum value between all the abscissas spectra minima, and the maximum
corresponds to the minimum between all abscissas maxima. They may be changed
by the user. The user should also supply the calibrating coefficients
a,b,c. By using the
button, the XAID_CALIB application is started to help
in finding the coefficients. The coefficients found in this way are automatically
transferred to the DELIA window. Once all parameters are filled, press
the
button to make calculations
over all spectra. The results appear in the "Result:" text window
and also in a newly created XPlot window. The results can be visualized
or exported using the "Plot
results" buttons.

- Phase III [chi(k)]: extraction
of the XAFS signal, i.e., calculate Chi(k) from Mu(Energy)
over all the spectra. For selecting the appropriate parameters for the
extraction, the user must perform interactively the extraction on a single
spectrum (select its index and then press the Go button to start XAID_MU2CHI
module. The parameters of the extraction are copied automatically to their
respective boxes.

- Phase IV [Fourier]: Fourier
transform and filtering. As in the previous phase, the user must first
perform the Fourier Filtering on a single Chi(k) spectrum, by using
the XAID_FF module.
The parameters are copied automatically.

