Ion bombardment induced photon and secondary electron emission

Abstract

Results of an experimental investigation of photon and secondary electron emissions produced during inelastic collisions between energetic ions and lattice atoms are reported. Cs and Na ions, accelerated to energies of 1 to 20 keV, were used to bombard Al, Au, Cu, Cr, Fe, Ge and Si targets. Alkali metal ions were selected since they have no potential secondary electron emission and direct comparisons between photon and electron emission were possible. The photon emission observed was that of the line spectra of neutral atoms and no continuous spectra, or plasma oscillation emission, was observed. The intensity of photon emission was inear with the ion beam current density up to 10 μA/cm 2 for cesium and 1 μA/cm 2 for sodium ion bombardment. Above these current densities a saturation, which is not explained, occured. The photon emission intensity increased with ion energy up to approximately 10 keV where a saturation occurred. Target self-absorption of the emitted photons accounts for this saturation, however. The dependence of the photon emission and the secondary electron emission upon experimental parameters was similar, but not identical. Both emissions originate in inelastic collisions although their means of escape from the target affects their dependence upon experimental parameters.