Charge state dependence of copper L-shell x-ray production by 4-14 MeV oxygen ions

Charge state dependence of L-shell x-ray production cross sections in Cu-29 bombarded by 4-14 MeV O-8(q+) ions with charge states from q = 3+ to 8+ was measured using a Si(Li) x-ray detector with a resolution of 96 eV at 1 keV. An ultra-thin copper foil was used to ensure single-collision conditions. The data for the total L x-ray production cross sections are compared to the predictions of the first Born and the ECPSSR calculations for L-shell ionization converted to x-ray production cross sections using a single-hole fluorescence yield. Except at the lowest projectile velocity, the ECPSSR theory gives satisfactory agreement with the data while the first Born theory overpredicts all the data in the investigated energy range by almost two orders of magnitude. Measurements of the charge state dependence of the target L-shell x-ray production cross sections allowed the separate contributions of the electron capture (EC) and the direct ionization (DI) to the inner-shell ionization to be determined. The EC contributions were extracted from the x-ray measurements with two, one, and no K-shell vacancies in the oxygen ions. These EC cross sections are compared with the results of an OBK approximation and the ECPSSR theory, and found to be significantly smaller than both EC calculations.