Mott scattering

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Mott scattering, also referred to as spin-coupling in elastic Coulomb scattering, is the separation of the two spin states by scattering an electron beam off the Coulomb field of heavy atoms. It is mostly used to measure the spin polarization of an electron beam.

In lay terms, Mott Scattering is similar to Rutherford Scattering but electrons are used instead of Apha Particles as they are a lot (around 4 orders of magnitude) smaller. This enables it to penetrate the atomic nucleus giving valuable insight into the structure of a nucleus.

The electrons are often fired at Gold foil because of its high Z, because it is non-reactive (does not form an oxide layer), and because thin gold films which reduce multiple scattering, are easy to produce. The presence of a spin-orbit term in the scattering potential introduces a spin dependence in the scattering cross section. Two detectors at exactly the same scattering angle to the left and right of the foil count the number of scattered electrons. The asymmetry A given by: $A = \frac{I^{right}-I^{left}}{I^{right}+I^{left}}$ is proportional to the degree of spin polarization P according to A = SP, where S is the Sherman function.

[edit] References

J. Stohr & H.C. Siegmann, Magnetism – From Fundamentals to Nanoscale Dynamics (Springer, 2006)
T.J. Gay & F.B. Dunning, Rev. Sci. Instrum. 63, 1635-1651 (1992)
Hyperphysics [1]