KINEMATIC ANALYSIS OF RADIATION FROM ATOMS AFTER ELECTRON-IMPACT EXCITATION

The polarization of the emitted photon from an atom or ion after electron-impact excitation is related to that of the incident electron by making use of rotation and parity symmetries. Explicit formulas for the angular distribution and polarization of the photon are derived in terms of angle-independent dynamic parameters by using the helicity formulation of the collision processes. Physical interpretations of the five independent dynamic parameters in the electric dipole approximation are presented. Conditions for emitting completely polarized photons are given.