Effect of oxide band structure on the emission process of excited atoms under ion bombardment

Ion-photon emission (IPE) was investigated under Ar+ ion bombardment of magnesium aluminate spinel crystals of different compositions MgO · nAl2O3 (n=1.0; 2.5) and, for comparison Al-metal target. For all targets the only emission of metal excited particles was observed, which leads to lines of Al I, Al II, Al III, Mg I and Mg II spectra. It was revealed that quantum yield of the IPE of different lines were equal in the range of values 10-4-10-7 photon/ion and increases in 5-7 times of that originated from decay of atomic excited states with Eex≤4.83 eV for oxides to compare with metal. The main criteria, which determines the conservation of excitation in flying-off atoms or ions is relation between the band structure of target and energy level of corresponding exited state of emitting particles. Analysis of obtained data allows us to estimate the width of conduction band (μ) in spinel: 0.995 eV≤μ≤1.16 eV. There was suggested the new approach for description of energy distribution of emission of knocked out excited particles. The best agreement of calculated data with experimental ones was obtained when the contribution of both the cascade collisions and surface recoil processes of primary ions in solids are included to generate flying-off excited particles