Scanning Microscopy


Digital imaging with cathodoluminescence (CL) capability, provides an additional, quantitative imaging perspective. While CL images can be useful by themselves, most microbeam instruments allow simultaneous acquisition of other signals including backscattered electron (BSE), secondary electron (SE), and X-ray images providing a powerful set of data for interpretation. Digital panchromatic images allow the use of standard and advanced image processing now available on laboratory computers to enhance single images or provide a means of combining information from two or more images. Other advantages of digital CL images include: 1) selective scan rates to avoid image distortion; 2) adjustable dwell times at any point to collect sufficient light due to weak CL; 3) calibrated image scales allowing relocation of features for additional study.

Many minerals and synthetic phases show CL and these images often reveal textures either difficult or impossible to observe with other signals. Examples of digital CL images are presented for: 1) diamond, where complex internal textures are revealed including the presence of features possibly corresponding to giant platelets; 2) forsterite from the Allende meteorite where CL reveals complex zoning within single grains the intensity of which correlates with the Al and Ti; 3) terrestrial carbonate showing intricate banding, the intensity of which can be compared with X-ray images; 4) meteoritic melilite where the CL reveals complex zoning and intensity variation within minor included spinel phases.

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