Cathodoluminescence Explained. Episode 3: Analysis Modes for Geoscience Applications
Cathodoluminescence (CL) microscopy—the analysis of light emitted by a mineral or gemstone when excited by an electron source, typically a scanning electron microscope (SEM)—has proven to be a very effective microanalysis tool used to understand our geological history. Amongst other things, CL analysis is used in geochronology studies in determining zonation and late rims in zircons, revealing overgrowth, cementation, and fluid flow processes in metamorphic rocks, and, more recently, thermobarometry in petrographic samples through quantitative analysis of trace element distributions.
Using the electron beam of the SEM, CL images or maps are collected to reveal spatially resolved information about the sample under investigation using a light-sensitive detector. In its simplest form, the CL detector may be a diode or photomultiplier tube (PMT) that measures the intensity (flux) of light emitted as a function of position of the electron beam. However, the emitted light may be described by the distributions in wavelength (color), polarization or emission direction (angle), some or all of which may provide critical information in characterizing a sample. Unfortunately, an ideal detector that provides a complete understanding of the emitted light distributions over a wide field of view, at high resolution(s) and with the highest sensitivity is not possible within the laws of physics. Instead, CL detectors must sacrifice performance in some areas in order to enable optimized detection in others. In this webinar, we will review the different hardware and analysis modes available in CL detectors, discussing the benefits and drawbacks of each when analyzing geoscience specimens.
David Stowe D.Phil., Product Manager, Gatan