Nondestructive Full-Field Imaging Xanes-Peem Analysis Of Cosmic Grains

For chemical analysis of submicron particles, mass spectrometric methods have the disadvantage of being destructive. Thus, a nondestructive elemental and chemical mapping with a high spatial resolution prior to mass analysis is extremely valuable to precharacterize the sample. Here, first results are presented of combined XANES (x-ray absorption near-edge structure) and PEEM (photoemission electron microscopy) measurements on a cosmic grain fraction from the Murchison meteorite. This nondestructive full-field imaging method is well suited for a quantitative analysis and for a preselection prior to detailed mass spectrometric investigations with isotopic resolution/selectivity. A spectral unmixing algorithm helped to distinguish between elements in different binding surroundings and therefore to obtain lateral information about the elemental composition and the chemical structure. Individual Al2O3 and SiO2 grains as well as Cr-rich grains could be identified among the majority of SiC grains. This method is suited not only for meteoritic material but can in general be applied to composite grain materials of submicron sizes.