Coherence and correlation in electron scattering from the alkalis

A series of superelastic electron scattering experiments from lithium and from potassium is described in which the total polarisation parameter P+ is measured. We report significant departures from the coherence condition P+ = 1 for both targets. The structure observed in the parameter P+ can be interpreted by a qualitative wave mechanical model that had been introduced by our research group to explain similar structure in superelastic electron scattering experiments from sodium.