Data fusion of LIBS and PIL hyperspectral imaging: Understanding the luminescence phenomenon of a complex mineral sample.

Laser-induced breakdown spectroscopy (LIBS) imaging is an innovative technique that associates the valuable atomic, ionic and molecular emission signals of the parent spectroscopy with spatial information. LIBS works using a powerful pulse laser as excitation source, to generate a plasma exhibiting emission lines of atoms, ions and molecules present in the ablated matter. The advantages of LIBS imaging are potential high sensitivity (in the order of ppm), easy sample preparation, fast acquisition rate (up to 1 kHz) and µm scale spatial resolution (weight of the ablated material in the order of ng). Despite these positive aspects, LIBS imaging easily provides datasets consisting of several million spectra, each containing several thousand spectral channels. Under these conditions, the current chemometric analyses of the raw data are still possible, but require too high computing resources. Therefore, the aim of this work is to propose a data compression strategy oriented to keep the most relevant spectral channel and pixel information to facilitate, fast and reliable signal unmixing for an exhaustive exploration of complex samples. This strategy will apply not only to the context of LIBS image analysis, but to the fusion of LIBS with other imaging technologies, a scenario where the data compression step becomes even more mandatory. The data fusion strategy will be applied to the analysis of a heterogeneous kyanite mineral sample containing several trace elements by LIBS imaging associated with plasma induced luminescence (PIL) imaging, these two signals being acquired simultaneously by the same microscope. The association of compression and spectral data fusion will allow extracting the compounds in the mineral sample associated with a fused LIBS/PIL fingerprint. This LIBS/PIL association will be essential to interpret the PIL spectral information, which is nowadays very complex due to the natural overlapped signals provided by this technique.

Combining Laser-Induced Breakdown Spectroscopy with Molecular Laser-Induced Fluorescence.

We propose combining laser-induced breakdown spectroscopy (LIBS) with molecular laser-induced fluorescence (MLIF) with resulting plasma-borne molecules as a means of studying laser-induced plasma (LIP). Examples of this method with LIP-created Al, Si, and B monoxides are presented. Applicability of the LIBS-MLIF method for elemental and isotope analysis is demonstrated.

Industrial online raw materials analyzer based on laser-induced breakdown spectroscopy.

From its inception, laser-induced breakdown spectroscopy (LIBS) has been recognized as a prospective tool for online process control. Nevertheless, it took considerable time and effort to transform this potential opportunity into application in a working industrial system, such as the mining industry, under real-life conditions and a 24/7 operating mode. There were three main attributes of LIBS to prove: its advantage over other online techniques, mainly prompt gamma neutron activation analysis and X-ray fluorescence; its ability to give relevant data despite its surface but not volume analytical abilities; and its ability to be sufficiently accurate for online process control needs. Comparison of the quantitative results gained from industrial installations of an LIBS analyzer with results of conventional analytical methods and, most importantly, the substantial improvement of the technological process effectiveness proved that LIBS is in fact an excellent technique for online process control in the mining industry.

Fraunhofer-type absorption lines in double-pulse laser-induced plasma.

We studied the confocal double-pulse laser-induced plasma in the very beginning of its life. It was found that the second laser pulse fired 0.7 to 5 µs after the first pulse produces plasma which, during the first 0 to 20 ns, resembles solar configuration. There is a very hot and compact plasma core that radiates a broad continuum spectrum and a much larger and cooler outer shell. The light from the hot core passes through the cold outer shell and is partly absorbed by atoms and ions that are in ground (or close to ground) states. This produces absorption lines that are similar to Fraunhofer lines observed in the sun spectrum. The possibility to use these absorption lines for new direct and calibration free laser-induced breakdown spectroscopy analytical applications, both in laboratory and industrial conditions, is proved.