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Excitation of atoms by spin-polarized electron impact yields fluorescence that can generally exhibit both linear and circular polarization. For experiments where the scattered electrons are not detected, symmetry requires that the electron beam be spin polarized in order for non-zero circular polarization to be observed. Extensive theoretical and experimental investigations have been performed regarding fluorescence polarizations (Stokes parameters) resulting from spin-polarized electron impact excitation of atoms. Measurement of fluorescence polarization provides insight into the angular momentum coupling that exists in the atomic state of interest. It also enables the measurement of electron spin polarization and experimental benchmarking of theoretical atomic structure calculations.
In an extension of previous atomic investigations, fluorescence polarization from polarized electron impact dissociation and excitation of simple diatomic molecules is considered. Stokes parameters are presented for dissociated atomic transitions in H, D, and N. Rotationally resolved molecular Fulcher band transitions in H2 and D2, as well as partially resolved transitions in N2, are also presented. Non-zero circular polarizations are observed for both the dissociation and molecular excitation processes. For the rotationally resolved molecular transitions, lower circular polarizations are observed for higher values of rotational states.