X-Ray Production Efficiencies for K-, L-, M-, and N-Shell Excitation by Ion Impact

Abstract

AbstractA systematic study of the production of characteristic X-rays by both light and heavy charged particles has been made. Using protons in the energy range 70-200 keV, data have been obtained for twenty-one X-ray lines encompassing a wavelength region from 1.44 to 44.00 Å from K-, L-, M-, and N-shells of elements with 6 ≤ Z ≤ 92. Additional X-ray production efficiencies have been measured in the K-, L-, M-, and N-shells using incident H2+, He++, N++, O++, and Ar++ ions in the energy range 90-400 keV. The ion beams were obtained from a 300 kV electrostatic accelerator, and beam analysis was obtained using a 7 kilogauss analysing magnet.The data for proton excitation show that, for X-rays of a given wavelength, the X-ray production efficiency increases with the principal quantum number of the atomic shell being excited. These results contradict results reported by Sterk et al, but agree with results obtained earlier by Khan et al.The results also show that the use of heavy ions (z > 5; obtains X-ray yields which are orders of magnitude higher than a repredicted by the direct scattering theory as used for protons and alpha particles.Ion excitation of X-rays has been applied to the study of the oxidation kinetics of iron as part of a surface physics program. The wide range of target penetration depth as a function of both mass and energy of the ion has allowed us to study oxide film thickness as a function of oxidation temperature and impurity depth and concentration. Data are presented for protons and argon ions incident on high- purity ion with surface oxide films varying in thickness from 35 Å to 750 Å. Oxygen and carbon sensitivities to equivalents of fractional monolayers are routinely obtained using nondispersive analysis of the X-rays.