Helium Symmetric (e,2e) Data

- Excess Energy = 3eV -

page prepared by

Andrew Murray (25th July, 1996)

3eV excess (e,2e) graph

Figure 1. The (e,2e) Differential cross section for an incident electron of energy 27.6eV (3eV excess energy) above the helium ionisation threshold.

For the above results the electrons were detected with equal energy and at equal scattering angles.

Theresultshavebeen parameterised in terms of the irreducible basis set that is used to fit all of the data taken at Manchester. This allows the results to be presented using a common 'language'.

The results have been normalised to unity at the common normalisation point at 90 degrees. Deviations from the expected Wannier model are already evident at this energy., especially at geometries away from the perpendicular plane, which still have an approximately Gaussian angular distribution.

The parameterisation again allows a 3-D picture to be established of the differential cross section surface, where the surface is traced out by the magnitude of the differential cross section at a given detection angle (theta, phi) around the scattering geometry.

Figure 2 shows the result of this 3-D fitting to the data presented above.

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