Excitation of the Na 3p state by proton impact

The proton-induced 3s-3p excitation of spin-polarised Na atoms has been studied both experimentally and theoretically. The total excitation cross section as well as the Stokes' polarisation parameters of the fluorescence light were measured in the regime of intermediate impact energies (0.8-6 keV). The measured circular polarisation P₃ is in accordance with conservation of spin orientation during the collision. The linear polarisation P₁ reflects the collisional induced alignment of the 3p state. The measured total cross section and the alignment are compared with various calculations. The p+Na collision system can be treated as a single active outer electron in the field of two inert cores.