Polarization of atomic line radiation

Abstract

In order to test the predictions of the general theory for the polarization of atomic radiation excited by electron impact, we measured the polarization of atomic lines in electron-alkali atom crossed-beam experiments. The results show a typical behaviour for the polarization of lithium and sodium resonance lines, which is contrary to the earlier measurements such as those ofSkinner andAppleyard: the polarization of the resonance lines increases monotonically from higher energies to the excitation threshold. The threshold polarization of the first resonance lines of Li⁶, Li⁷ and Na²³ is in good agreement with the calculations byFlower andSeaton. These results demonstrate that polarization is very sensitive to the natural level width, and to the fine and hyperfine structure separations of the excited states. Polarization of further lines has been investigated: an alkali line from anS to aP state is unpolarized as expected, but the polarization of a line from aD to aP state decreased in an unexpected manner near the threshold energy.