Influence of the resonant Raman scattering on XRF

HÉCTOR JORGE SÁNCHEZ; MARÍA CECILIA VALENTINUZZI

Córdoba, Argentina (SARX), Campinas, Brasil (RAU)

Congreso; IX Seminario Latinoamericano de Análisis por Técnicas de Rayos X, (SARX 2004) y en RAU 2005; 2004

XRF spectra exhibit, in some cases interesting features mainly due to scattering processes, one of these being the resonant Raman effect (RRS). It is an inelastic scattering process that occurs when the incident energy approaches from below to the absorption edge of the target element and can produce x-ray peaks interfering with the fluorescent one. The Raman scattering dominates the background behaviour of the fluorescent line and limits the achievable sensitivity for the detection of low concentration contaminants, specially for the detection of elements with proximate atomic number. The resonant Raman effect is responsible of the differences between the measured values of the mass attenuation coefficients and the corresponding theoretical values (of the order of 5-10%) when monochromatic x-ray beams interact with materials under resonant conditions. Synchrotron radiation was used to study the Raman effect on pure samples. The Raman peak has a non-symmetric shape and theoretical models for the differential cross section, convoluted with the instrument function, had to be used. In this way, RRS yields were obtained. Finally, the possibility of observing chemical link effects by studying the RRS peak shape and the corresponding energies is analyzed.