NEAR-THRESHOLD EXCITATION OF THE RESONANCE lambda 158.6 nm LINE IN ELECTRON-INDIUM ION COLLISIONS

Near- threshold electron- impact excitation of the resonance In+ ion 5s5p(1) P (o)(1) -> 5s(21)S(0) (lambda = 158:6 nm) line is studied using a spectroscopic method and a crossed (at right angle) monoenergetic electron and ion beams technique. Strong resonance features observed in the energy dependence of the eff ective excitation cross-section for this line are due to the emission of the dielectronic satellites 4d(10)5s5p(P-1(1)o)np -> 4d(10)5s(2)np of the resonance line below threshold and resonance excitation due to the electron decay of the autoionizing states above threshold. At the threshold of the resonance line excitation the radiative decay of the autoionizing states affects significantly both the shape and the value of the effective excitation cross- section.