Comparison of XRF and Raman Spectroscopy

Raman spectroscopy is an excellent spectroscopic analysis technique which is used to produce information related to the chemical structure, phase, polymorphism, crystallinity, and molecular interactions of the sample. This information, obtained by Raman spectroscopy, can be added with XRF to obtain better elemental information of the samples.

In Raman spectroscopy, an intensive beam from mono-energetic optical light source is used for inelastic scattering from the sample molecules. During the scattering process, the energy loss depends on the energy levels of the scattering molecule. Therefore, the Raman analysis method is used for the investigation of the energy levels of outer electron shells. These levels provide information on the atomic and molecular compositions of the materials. Using laser radiation sources of different energy ranges, Raman spectroscopy (in particular, μ-Raman) provides the possibility of focusing the light on small sample areas, which allows study of the sample materials identical to μ-XRF.

A model for combining XRF and Raman spectroscopy has been prepared to test the possibility for the measurement of the constituents of sample materials. The μ-XRF setup was created using a micro-focus tube with an Rh-target, polycapillary optics, and SDD. It was possible to mount the sample on a three-dimensional motorized stage, and simultaneously observe the sample by using an optical microscope. It was also used to focus the incident laser light on the sample surface (particularly 633 and 785nm).

The laser light and the Raman-spectrometer were connected to the microscope using optical fibers. This model can be seen in details elsewhere and can be used for several kinds of analysis to investigate pigments and to analyze geological samples. The methods used here are quite different in terms of measurement strategies and data interpretation, which requires thorough and deep understanding in order to get correct analytical results. Their use will certainly expand into all sorts of research areas. In addition, these instruments can be relatively affordable while also being non-destructive and easy to use.