The LIBS microscope has the capacity to provide fast elemental mapping of flat surfaces, typically cross sections of geological samples, marine shells, bones, teeth etc. The 2D-elemental profile of the mapped surface can be used to identify the distribution of mineral phases in rocks, to measure the variability of elemental proxies related to paleoenvironment in shell studies or to assess the diffusion of environmental pollutants into hard tissues. In the present micro-LIBS workstation a Q-switched Nd:YAG laser is used (λ = 1064 nm, pulse duration: 10 ns, pulse energy 5-20 mJ). The laser beam is focused on the sample through a laser objective lens. The spot analysed by each pulse has a diameter in the range of 40-60 μm. The light emitted by the plasma is transferred via an optical fiber to the spectrometer which captures LIBS spectra for each one of the laser pulses that scan the surface. According to specific analysis requirements the spectral data is processed on-line or following completion of scanning. Samples are mounted on a motorized X–Y–Z micrometric stage and translated with respect to the laser focal spot that remains fixed in space. The typical translation step is on the order of 100 μm. A CCD camera enables the user to have a clear view of the sample surface and to define the area that is to be mapped (any shape is acceptable). A typical elemental map of 5000 “pixels” is obtained in about one hour.
Characterization of the elemental composition of different types of materials, icluding the cases of laser cleaning diagnostics and determination of stratigraphies. μ-LIBS has been employed in the analysis of archaeological and historical objects, monuments and works of art for assessing the qualitative, semi-quantitative and quantitative elemental content of materials such as pigments, pottery, glass, stone, metals, minerals and fossils. Recent developments that combine μ-LIBS with microscopy and raster scanning have enabled micro-analysis of surfaces, for example sections of rocks or mollusk shells, providing rapid 2D-mapping of the element distribution across the sample surface.