Analysis of Cd and Ag clusters by concurrent standard and high-resolution micro-PIXE spectroscopy

Abstract

Particle Induced X-ray Emission (PIXE) spectroscopy is now a mainstay in Ion Beam Analysis (IBA) and is applicable across several scientific disciplines requiring high sensitivity for detecting constituent elements in a material. While the technique is well established, the use of conventional broad-band spectrometers limits the ability for X-ray line separation for closely lying characteristic energies. The inability to separate closely lying X-ray lines using standard silicon detectors with resolution >120 eV FWHM (for Mn Kα) especially hinders quantitation in varying applications. One such limitation is the separation of Ag and Cd L-shell X-ray lines, the extraction of which is often needed for accurate concentration measurements. While this limitation may be circumvented by using higher proton energies (>15 MeV) for Ag and Cd K-shell excitation, accurate computation may still be constrained by the lack of X-ray production cross section data, as cross sections predicted by theory are only widely validated up to 3 MeV. The present work demonstrates a simultaneous use of high-resolution and standard PIXE spectroscopy using 2 MeV proton beams for the measurement of relative Ag and Cd L-shell concentration ratios, along with the use of multivariate analysis of PIXE spectral images. Ag and Cd concentration ratios analysed using GUPIXWIN for standard PIXE and a Wavelength Dispersive X-ray Spectrometer (WDX) are compared and discussed.