Large database of high resolution Kβ X-ray emission spectra of selected 3d metal (Ti, V, Cr, Mn) compounds obtained after excitation by 2 and 3 MeV proton beams have been built. Analysis of (relative) positions and intensities of Kβ′′ and Kβ_2,5 X-ray contributions as a function of chemical and structural properties of analyzed 3d metal compounds have been performed. Two independent experiments employing wavelength dispersive spectrometers with different experimental resolutions (8.1 eV versus 2.8 eV for the case of Cr Kβ_1,3 line FWHM) were performed in order to exclude any possible effect of the experimental resolution on the extracted values. A simple parametrization of Kβ′′ and Kβ_2,5 X-rays' relative positions and intensities over the range of 3d metal compounds with various oxidation states, a wide range of metal–ligand bond lengths, and selected 3d metals, was performed. Results of our parametrization were compared critically with other experimental and theoretical values available in the literature. The parametrization obtained in this work could be used for chemical and structural speciation of 3d metal compounds and for improved interpretation of K X-ray spectra of 3d transition metal compounds measured by solid state detectors.

A downsized wavelength dispersive X-ray spectrometer, employing a flat crystal and a CCD detector for use with focused ion beams has been constructed and employed to study ion beam induced chemical effects in Si K X-ray spectra from silicon and its selected compounds. By using ADP, PET and LiF(110) diffraction crystals, the spectrometer can measure X-rays in the energy range between 1.2 and 8.4 keV, with the energy resolution E/ΔE(FWHM) = 1850 on Al Kα and 1580 on Si Kα achieved with 2 MeV protons. This energy resolution enables the study of secondary effects in the K X-ray spectra of light elements, L-shell spectra of medium Z elements and M-shell spectra from heavy elements. The K X-ray spectra of silicon and selected silicon compounds were measured after excitation with 2 MeV protons and 20 MeV carbon ions focused to micrometer size. The results obtained for peak relative intensities were analyzed to study their dependence on the silicon oxidation states and effective charge on Si. The results were compared with the existing data obtained by proton, electron and photon induced ionization mechanisms, and clear differences between the ionization sources were observed. Si Kα multiple ionization satellites were studied with 20 MeV carbon ions on Si, SiO₂ and SiC. The variation of apparent average L vacancy fraction p_L ^x with effective charge on Si was studied. It has been shown that, for ionization by 20 MeV carbon ions, the relative KαL² intensity is more sensitive to the chemical environment compared to p_L ^x values.

In this work, we demonstrate the usefulness of multivariate techniques for the analysis of two-dimensional (2D) spectral images obtained by proton beam ionization (PIXE mode) and combined proton beam and photoionization with an X-ray tube (PIXE + XRF mode). Two different multivariate analysis approaches were used: (i) principal component analysis (PCA) for dimensionality reduction followed by k-means clustering for the identification of different sample regions and (ii) t-distributed stochastic neighbour embedding technique (t-SNE). In PCA + k-means clustering, similar pixels were grouped into different clusters where a direct connection between individual clusters and elements identified from cluster spectra resulted in the fast image segmentation and identification of different sample regions. t-SNE was used for dimensionality reduction and simple 2D visualization of high dimensional data. Three different cases were investigated: (i) qualitative analysis of 2D spectral maps having pixel spectra with a high number of counts per pixel in the full range of measured X-ray energies collected in PIXE + XRF mode excitation, (ii) qualitative and semi-quantitative analysis of 2D spectral maps having pixel spectra with medium to low counts per pixel collected in PIXE mode, and (iii) qualitative and quantitative analysis of 2D spectral maps having medium to low statistics per pixel obtained in PIXE mode. In the actual case studies, we identified all the pigments in artificial and real samples, namely, illumination from a historical book, and quantitatively characterized the identified gold layer and Niello decoration on an archaeological plate of Roman origin. In the last example, we were able to identify the sample regions with similar layer thicknesses and obtain the layer thickness and elemental concentrations. We demonstrated that high statistics spectra that would contain enough information for qualitative and/or quantitative analysis of major, minor and even trace elements can be deduced using multivariate analysis methods even from low-statistics individual pixel spectra collected during 2D scanning of objects under investigation. This could be of particular importance for sensitive samples that could be damaged during long irradiation.