H~+ and He~(2+) induced W L X-rays intensity ratios: Part I, Si(Li) data and EDS high resolution insight

摘要

Recently, the authors have presented experimental evidences that for some energy windows, proton-induced W L shell X-rays intensity ratios of transitions to L_1 subshell depend on the ion beam energy and on the chemical species even after known matrix effects are subtracted. These results, which put in question the assumption of the invariance of the relative intensity of X-ray transitions to the same atomic subshells, are further exploited in this work, where more data for three different W compounds (W, Li_2WO_4 and P_2O_5.24WO_3.xH_2O) are presented followed by a detailed study using an ultra-pure (99.995%) W thick foil, used to avoid any possible target contamination interference on the results. Samples were irradiated by H+ beams in various conditions in the energy range between 0.25 and 2.38MeV and by He~(2+) beams having energies between 3.5 and 5.0MeV. Spectra were collected using the Si(Li) detector at CTN 2.5MV Van de Graaff standard Proton-Induced X-ray Emission (PIXE) set-up as well as using the Energy Dispersive Spectrometry (EDS) high resolution X-ray microcalorimeter spectrometer (XMS) at CTN 3.0MV Tandetron accelerator high resolution high energy (HRHE) PIXE end station. Results were normalized to the theoretical intensity ratios and plotted as function of the ratio of collision characteristic times allowing the comparison of H+ and He2+ results. W L X-rays intensity ratio variations are presented and compared with theoretical expected results. Radiative Auger emission transitions observed in an EDS high resolution XMS spectra are shown to probably play a crucial role in the highly unexpected results obtained for intensity ratios of transitions to the same subshell.