Polarized fluorescence by the electron impact excitation of atoms
Eves, Brian John
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Polarized radiation emitted by electron impact excited atoms carries information about the anisotropic population of the magnetic sublevels. An overview of the theory necessary to describe the time evolution of an electron impact excited atom, and therefore the emitted radiation, is presented and applied to three cases. The three cases include the 1s4d-1s2p-1s$\sp2$ cascade transition in helium, the s4d-3s3p-3s$\sp2$ cascade transition in magnesium, and the electron impact excitation off of a laser excited P-state to a D-state and subsequent re-emission back to the P-state. The apparatus required to measure the helium, and magnesium cascade transitions has been built. The apparatus consists of an electron gun aimed at an atom vapour beam. The emitted radiation was detected by two photon detectors, one for each level transition. The equipment is tested by comparing the measured polarization of the 1s4d-1s2p transition in helium to existing published data. The polarization of the 3s4d-3s3p transition in magnesium has also been measured. The coincidence measurements required to complete the determination of the magnetic sublevel populations of the D-state for helium, and magnesium have not yet been made.