LIBS (laser-induced breakdown spectroscopy) technology is at the heart of all ELEMISSION analyzers. It’s thanks to the LIBS process that ELEMISSION analyzers can detect, identify and classify or quantify the chemical composition of any material, regardless of its state (gas, liquid, solid, conductive or non-conductive). The recent success of the LIBS probe on the Curiosity and Perseverance Mars rovers has renewed interest in this technology for many applications, particularly in geology and geochemistry.
How does LIBS work?
THE LASER PULSE
LIBS is a laser ablation technique for which photons are emitted by the laser-generated plasma. LIBS combines all the necessary processes for atomic emission spectroscopy simultaneously: sample vaporization, atomization, and excitation. A LIBS measurement is performed by first generating the plasma at the sample surface and then collecting the emitting light spectra.
The advantage of sampling a large surface area of a solid is that its average composition can be accurately estimated. Analysis speed is an important parameter for fast access to signals that approximate the average sample composition. Until very recently, the acquisition speed for LIBS was limited to less than 20 measurements per second (20 Hz). The work of Rifai et al. demonstrated it would be possible and useful to use an acquisition frequency of 1,000 measurements per second (1,000 Hz). This high acquisition frequency makes possible the study of the multi-element spatial distribution on the sample’s surface for bigger samples, such as drill cores.
LIBS hyperspectral imaging
THE POWER OF HYPERSPECTRAL EMBEDDING
LIBS microanalysis is currently a particularly active field of application in recent literature. Until recently, LIBS sample analysis consisted of effectively accumulating analytical signals without paying much attention to the spatial distribution of elements on the surface of the sample. It was standard practice to assume sample uniformity on a macroscopic/millimetric scale if a large enough area was sampled. However, microanalysis by LIBS reveals surprising information about the surface uniformity of a solid sample. In fact, spatial information can be used to understand several physio-chemical phenomena on the history of the sample’s forming, or any other property derived from it. Furthermore, LIBS tomography is a leading tool for the study of solid samples' three-dimensional structure.
The hyperspectral embedding is very interesting because each spot samples can be attributed to a single phase (or mineralogy) with subtelties explained by the elemental content. Using pattern recognition algorithms, a database of typical spectra for a single phase are used in the identification process. When all spots are identified, a map is generated. The ultimate asset of LIBS analysis is that each spectra is complex enough for pattern recognition and rendering the multi-elemental content in real-time, therefore it is possible to generate a map of elements disseminated within single mineralogies.
THE ULTIMATE TECHNOLOGY FOR IDENTIFICATION
Because all elements have a high atomic emission signal, all of them can be analyzed using LIBS technology. An interactive periodic table of the elements analyzed using the ELEMISSION technology and examples of their significative spectra and imaging is illustrated below. All elements in red were successfully analyzed. The elements in grey are analyzable, but were too hazardous/unstable or have not yet been the main focus of a project.