Fluorescent Spectroscopy of Mineral and Material Samples

Abstract Wavelength dispersive spectrometry of long wavelength lines by EPMA can give information on the site symmetry and bonding of the x-ray-emitting atom. For fully focussing spectrometers, the energy resolution can be as high as 2eV or better at a spatial resolution of 1 μm, but electron beam currents often must be set to damaging levels. Fluorescent spectroscopy of the same lines in the commercial laboratory XRF spectrometer is far less damaging but spatial resolution is non-existent or, with collimators, relatively poor. With a combination of electron induced and x-ray induced fluorescent spectroscopy, and the insight provided by molecular orbital calculations, speciation or state analysis can be achieved even on damage prone specimens. Electron and x-ray induced fluorescence has been employed to investigate surface coatings on magnesium metal. Oxygen Kα spectra for crystalline MgO, MgCO3 and powdered 4MgCO3.Mg(OH)2.5H2O were recorded using a TAP(2d=2.5757 nm) analysing crystal on a JEOL 8900R EPMA and a Philips PW 1404 XRF.