ASAXS

Overview:

The normalized intensity measured at a minimum of three energies can be decomposed into the energy-independent normal SAXS term, a cross-term involving the amplitudes of normal SAXS and the resonant scattering of the counter-ions, and the resonant scattering term due to the counter-ions.

This can be achieved using the quadratic method proposed by Ballauff et al., neglecting the often very small contribution of f'' below the absorption edge.

Alternatively, the (overdetermined) system of equations for at least 3 measured energies can easily be solved numerically (matrix method). The latter method can also be used for energies where the contribution of f'' cannot easily be neglected (i.e. at energies above the absorption edge).

Both techniques are implemented in SAXSutilities.

Description:

- choose directory

Select your data directory or type it directly in the corresponding input box. - file selection

Select the data to be decomposed. Use the according input box to filter the file list. You have to use wildcards. Use update list to activate the filter or to update the file list.

The files have to contain the measured energy in form of 5 digits without comma. The character position of the first digit has to be specified at the bottom of the GUI. - anomalous scattering factors

A file with the anomalous scattering factors f' and '' has to be supplied. The Setup menu contains an option if the scattering factors are used as tabulated or if the energy resolution of the beamline ID02 is taken into account. - decompose

Starts the decomposition. Two methods are used:

1. fit of a quadratic function as proposed by Ballauff et al. and

2. matrix method.

For more details, please refer to:

Instrumental developments for anomalous small-angle X-ray scattering from soft matter systems

M. Sztucki, E. Di Cola, and T. Narayanan

J. Appl. Cryst. 43, 1479-1487 (2010)

During the splitting the both graphs visualize the quality of the calculations for each analysed q value (see screenshot above).

The lower graph shows the fit of the quadratic function, the upper one shows the comparison of the measured data with the result of the matrix solution. A value close to 1 at all measured energies is a sign for good quality.

At the end of the calculation the three partial intensities are visualized (see screenshot below).

- help

Shows this help. - close

Closes ASAXS application.

Available menu options:

data menu:

Self explaining...

setup menu:

Choose if the anomalous scattering factors will be used as tabulated, or a correction for the energy resolution of beamline ID02 (default) will be applied.

programs menu:

Start other programs of the SAXSutilities package.

help menu:

Get (this) help and updates.