Photon-scattered-atom coincidence study on K-He with vector polarisation analysis

The linear and circular polarisation of the K(4 2 P to 4 2 S) photons detected in delayed coincidence with the inelastically scattered K atoms are presented for K-He collisions at 93 eV as a function of the scattering angle. Data are analysed in terms of the Stokes parameters, and the coherence properties of the excitation process are examined. It is concluded that spin dependent forces do not play an important role in the excitation process. The lambda and chi parameters are also derived. Simple models for the excitation process are discussed in order to explain the impact parameter dependence of chi .