Once GudrunX has been successfully run, the data can be viewed in gnuplot. A program for plotting the data can be run from GudrunX through Plot → 'Generate gnu plotting file'
In the plotting window you can add files, specify the y data which you would like to plot and alter the pen colour.
The output files from GudrunX which need to be viewed to assess the quality of the S(Q) are
- .subcan - this file contains many rows of data but the 1st y data set gives the experimental data (red), the 2nd contains the form factor data (green) to which the experimental data is scaled, and the 6th is the calculated bremstralung (blue).
- .soq- this file contains the sharpened S(Q) data and the statistical error.
- .gofr - if the option to calculate g(r) is selected, then a very rough g(r) is given in this file. This can be quickly used to assess the quality of the data.
The data shown here has been well corrected, S(Q) oscillates around zero and there is no positive or negative residual peak from the silica capillary in G(r). Your first attempt will probably not look this good, and experimentation and patience is required to improve the outputs. To improve S(Q), the most likely variables which will need altering are the effective density and the multiple scattering. If you cannot extract a good S(Q) by altering these two values, then consider varying the level of fluorescence (increasing it from zero) and the bremsstrahlung correction (altering it from the starting value of 0.55). These changes should be done with caution.
You should not change the compton scattering factor or the polarisation.
If there is a noticeable peak at ~1.6 Å which should not be present, vary the amount of container scattering which is being subtracted from the experimental data. If your data contains elements which will result in bond lengths similar to those of Si-O, this corrections will be more difficult perform, and you should be cautious when interpreting the data. For advice, contact your instrument scientist.