Excitation of He and Ne 3p states by polarized electrons

Integrated Stokes parameters for the transitions in helium (388.9 nm) and neon (640.2 nm) and (626.7 nm) have been measured over the electron energy range from threshold to 300 eV after excitation by polarized electrons. The measured zero values of for both the He 388.9 and Ne 640.2 nm photons are consistent with the LS coupling of the upper states for each transition. Similarly, the measured non-zero values of for the 626.7 nm photons provide clear evidence of the breakdown of LS coupling for the Ne state due to the spin - orbit interaction of the atomic electrons.