Balmer line polarization induced by electron and proton impact on atomic hydrogen

This study investigates the collision induced excitation of atomic hydrogen into the n = 3 state with respect to the linear polarization fraction of the Balmer line. We used electrons with energies between 80 eV to 3 keV, protons and singly charged helium ions in the energy range from 40 keV to 1 MeV. Differences for electron and ion excitation at equal velocities could be explained within a first Born approximation. Comparisons with theories for electron and ion impact are discussed.