Coherence and correlation in electron scattering from the alkalis

A series of superelastic electron scattering experiments from lithium and f rom 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 int erpreted by a qualitative wave mechanical model that had been introduced by our research group to explain similar structure in superelastic electron s cattering experiments from sodium.