The polarization properties of excited alkali atoms having suffered half collisions with noble gas atoms following excitation by nonresonant photon absorption during a strong collision, are investigated. On the basis of a semiclassical perturbation treatment of the density matrix up to second order in the driving field a general expression for the polarization dependent intensity of the emitted alkali fluorescence is derived. Assuming quasistatic excitation of the collision complex and considering reorientation of the orbital and spin electronic angular momenta within a cut off radius, explicit results for the polarization degrees are presented and discussed, depending on the initial molecular excited state and coupling case.
Electron-photon coincidences with initially polarized electrons have been measured for the first time. Results for linear and circular polarization components of the 254-nm line (Hg $6^{3}P_{1}\ensuremath{-}6^{1}S_{0}$ transition) are presented as a function of electron energy for electrons which are scattered inelastically (
63P1 excitation) in the forward direction. The analysis of these polarization components allows one to determine the role of spin-dependent interactions during collision as well as to determine the relative phase of the two scattering amplitudes involved.
We present linear and circular polarization measurements of $3^{1}P\ensuremath{-}2^{1}S$ (501.6 nm) photons detected in delayed coincidence with electrons inelastically scattered from the
31P level of helium. Vector polarization and coherence parameters of the coincident radiation provide direct experimental evidence of the coherent nature of the excitation process. Atomic orientation is obtained directly from the circular polarization measurements. Analysis of the data also yields $\ensuremath{\lambda}$ and $\ensuremath{\chi}$ parameters for
31P excitations, which are compared with previous data and theory.