Excitation of He 33P and Ne 3p states by polarized electrons

Integrated Stokes parameters for the transitions in helium 33P → 23S (388.9 nm) and neon 2p53p[2σ5]3 → 3s[2σ3]2 (640.2 nm) and 2p53p'[2σ3]1 → 3s'[2σ1]0 (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 P2 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 P2 for the 626.7 nm photons provide clear evidence of the breakdown of LS coupling for the Ne 2p53p'[23]1 state due to the spin-orbit interaction of the atomic electrons. Non-zero values of the Stokes P3 parameter induce strong electron exchange effects, particularly near threshold. Negative ion resonances show considerable effects on the polarizations of the subsequent radiations. The effect of different core configurations on the alignment of excited states is discussed. (Author)