Chemical state analysis of sulfur in samples of environmental interest using high resolution measurement of Kα diagram line

Abstract

The proton induced Kα X-ray emission spectra of pure and some compound targets of sulfur were measured with a crystal spectrometer in Johansson geometry, which enables energy resolution below the natural linewidth of the measured Kα line. From these measurements the absolute energies of the S-Kα 1,2 lines were experimentally determined. In addition, the energies of the KαL 1 X-ray satellite lines, appearing in these spectra as a result of the radiative decay of atomic states with one hole in the K shell and one in the L subshells, were also measured. The measured Kα diagram and satellite line energies depend crucially on the S chemical state. The measured diagram line energies, as well as their relative intensity ratios obtained from the X-ray spectra of different S compounds, allow the deconvolution of X-ray spectra of mixed targets containing two different S compounds and the accurate determination of their mass ratio. Finally, the proton induced S-Kα X-ray spectrum from an aerosol sample was collected and the measured energies of the Kα 1,2 lines were used to specify the chemical state of S in the aerosol as a sulfate ([SO 4] 2−). In conclusion, the results of the present paper demonstrate that the S-Kα 1,2 emission energies depend on the S chemical state and, therefore, their determination allows the chemical state speciation of S in a given sample.