CHEMICAL-ANALYSIS; PULSE; PLASMA; PRESSURES; SEAWATER; WATER

The exploitation and research of deep-sea hydrothermal vent has been an issue of great interest in ocean research in recent years. Laser-induced breakdownspectroscopy (LIBS) has great potential for ocean application due to the capabilities of stand-off, multiphase, and multielement analysis. In this work, a newly developed compact 4000 m rated LIBS system (LIBSea) is introduced with preliminary results of sea trials. The underwater system consists of an Nd:YAG single-pulsed laser operating at 1064 nm, an optical fiber spectrometer, an optics module, and an electronic controller module. The whole system is housed in an L800 mm x Phi 258 mm pressure housing with an optical window on the end cap. It was deployed on the remote operated vehicle Faxian on the research vessel Kexue, and in June 2015 was successfully applied for hydrothermal field measurements at the Manus area. The obtained results are shown that the LIBS system is capable of detecting elements Li, Na, K, Ca, and Mg in the hydrothermal area. Profiles of LIBS signals of elements K and Ca have also been obtained during the sea trial. The results show that the K emission line is gradually broadened with depth from sea surface to sea floor (1800 m or so); the K intensity shows a hump shape with maximum value at about 1050 m. The Ca emission line is rapidly broadened below 400 m and slowly narrowed to the sea floor; the Ca intensity shows no obvious change below 400 m and increases continuously to sea floor. A very interesting finding is that the small fluctuations of intensity profile curve of Ca show a degree of correlation with seawater temperature change. The sea trial results prove the performance of LIBSea. After further optimization, it is hoped to apply the LIBS system to the in situ mineral deposits and hydrothermal vent fluid detection in deep sea. (C) 2017 Optical Society of America

INDUCED PLASMA SPECTROSCOPY; ATOMIC EMISSION-SPECTROMETRY; VACUUM-ULTRAVIOLET; SULFUR; STEEL; NANOPARTICLES; CALIBRATION; SAMPLES; RATIOS; SYSTEM

This work introduces a new approach to perform LIBS elemental imaging in the vacuum ultraviolet (VUV) wavelength range by using an argon purged probe coupled to a compact spectrometer. In spite of several important elements for geological and industrial applications such as S, P, As, B, C, or Zn presenting strong lines in the VUV range, the need for using specific optics and working under oxygen-free conditions has limited the extension of LIBS systems available for such a range. Herein, we present an adaptation of our LIBS imaging instrumentation to access the VUV while operating under ambient conditions. The proposed detection system is based on an optical probe directly coupled to a Maya2000Pro compact spectrometer (Ocean Optics), all purged with argon. The technical design along with a detailed evaluation of the VUV probe is addressed. The possibility of using this VUV probe for LIBS imaging is also investigated by studying a Canadian mine core sample with special emphasis on the detection of sulfur. In addition to sulfur, more than 15 elements including P, As, C, Ca, Si, Mo, B, and Zn have also been detected. Elemental images covering sample surfaces in the range of cm(2) with a micrometric spatial resolution (10 mu m) are presented. A detection limit of 0.2 wt% for sulfur is demonstrated in a single shot configuration. These results open new perspectives for both conventional LIBS and LIBS-based imaging in various application fields.

Baseline removal; Raman spectroscopy; laser-induced breakdown spectroscopy; LIBS; very near; infrared spectroscopy; VNIR;X-RAY-SPECTRA; LEAST-SQUARES; RAMAN-SPECTRA; NMR-SPECTRA; RECOGNITION; SUBTRACTION; REGRESSION; ALGORITHM

The task of proper baseline or continuum removal is common to nearly all types of spectroscopy. Its goal is to remove any portion of a signal that is irrelevant to features of interest while preserving any predictive information. Despite the importance of baseline removal, median or guessed default parameters are commonly employed, often using commercially available software supplied with instruments. Several published baseline removal algorithms have been shown to be useful for particular spectroscopic applications but their generalizability is ambiguous. The new Custom Baseline Removal (Custom BLR) method presented here generalizes the problem of baseline removal by combining operations from previously proposed methods to synthesize new correction algorithms. It creates novel methods for each technique, application, and training set, discovering new algorithms that maximize the predictive accuracy of the resulting spectroscopic models. In most cases, these learned methods either match or improve on the performance of the best alternative. Examples of these advantages are shown for three different scenarios: quantification of components in near-infrared spectra of corn and laser-induced breakdown spectroscopydata of rocks, and classification/matching of minerals using Raman spectroscopy. Software to implement this optimization is available from the authors. By removing subjectivity from this commonly encountered task, Custom BLR is a significant step toward completely automatic and general baseline removal in spectroscopic and other applications.

Laser-induced breakdown spectroscopy; Deep Sea; Double pulse; Cavitation bubble; High pressure;BULK AQUEOUS-SOLUTIONS; ELEMENTAL ANALYSIS; SINGLE-PULSE; SHOCK-WAVES; LIQUIDS; LIBS; EXCITATION; INTENSITY; ABLATION; INSIGHTS

There is a growing interest in the development of sensors use in exploration of the deep ocean. Techniques for the chemical analysis of submerged solids are of special interest, as they show promise for subsea mining applications where a rapid sorting of materials found in the sea bottom would improve efficiency. Laser-Induced Breakdown Spectroscopy (LIBS) has demonstrated potential for this application thanks to its unique capability of providing the atomic composition of submerged solids. Here we present a study on the parameters that affect the spectral response of metallic targets in an oceanic pressure environment. Following laser excitation of the solid, the plasma persistence and the cavitation bubble size are considerably reduced as the hydrostatic pressure increases. These effects are of particular concern in dual pulse excitation as reported here, where a careful choice of the interpulse timing is required. Shadowgraphic images of the plasma demonstrate that cavitation bubbles are formed early after the plasma onset and that the effect of hydrostatic pressure is negligible during the early stage of plasma expansion. Contrarily to what is observed at atmospheric pressure, emission spectra observed at high pressures are characterized by self-absorbed atomic lines on continuum radiation resulting from strong radiative recombination in the electron-rich confined environment. This effect is much less evident with ionic lines due to the much higher energy of the levels involved and ionization energy of ions, as well as to the lower extent of absorption effects occurring in the inner part of the plasma, where ionized species are more abundant. As a result of the smaller shorter-lived cavitation bubble, the LIBS intensity enhancement resulting from dual pulse excitation is reduced when the applied pressure increases. (C) 2017 Elsevier B.V. All rights reserved.

INDUCED PLASMA SPECTROSCOPY; CHEMCAM INSTRUMENT SUITE; VACUUM-ULTRAVIOLET; QUANTITATIVE-ANALYSIS; GALE CRATER; RADIATION CONDITIONS; STEEL ANALYSIS; SURFACE; MOLECULES; ROVER

Organic matter has been continuously delivered by meteorites and comets to Mars since its formation, and possibly formed in situ by abiogenic and/or biogenic processes, This organic matter may be preserved from the harsh oxidizing environment of Mars in specific locations. Together with water, organic molecules are necessary to the emergence of life as we know it. Since the first martian landers, scientists have been searching for organics and until today, only one positive detection has been made by a Gas Chromatography Mass Spectrometer (GCMS) instrument onboard the Curiosity rover. In this article we investigate a complementary approach to guide the search for organic matter using ChemCam, the first Laser-Induced Breakdown Spectroscopy (LIBS) instrument on Mars. This experimental study focuses on the analysis of carbon and nitrogen LIBS signatures in organoclay samples and allows the determination of the critical level (L-c) and limit of detection (LoD) of these elements with LIBS under Mars-like conditions, giving new insights into the search of organic matter on Mars. (C) 2017 Elsevier B.V. All rights reserved.

laser-induced breakdown spectroscopy; ChemCam; Mars Science Laboratory; trace elements; weathering; magmatic differentiation;INDUCED BREAKDOWN SPECTROSCOPY; MARTIAN SOIL COMPONENT; NORTHWEST AFRICA 7034; IN-SITU; INSTRUMENT SUITE; METEORITE; LITHIUM; MINERALOGY; TARGETS; WATER

The Chemistry Camera (ChemCam) instrument onboard Curiosity can detect minor and trace elements such as lithium, strontium, rubidium, and barium. Their abundances can provide some insights about Mars' magmatic history and sedimentary processes. We focus on developing new quantitative models for these elements by using a new laboratory database (more than 400 samples) that displays diverse compositions that are more relevant for Gale crater than the previous ChemCam database. These models are based on univariate calibration curves. For each element, the best model is selected depending on the results obtained by using the ChemCam calibration targets onboard Curiosity. New quantifications of Li, Sr, Rb, and Ba in Gale samples have been obtained for the first 1000 Martian days. Comparing these data in alkaline and magnesian rocks with the felsic and mafic clasts from the Martian meteorite NWA7533from approximately the same geologic periodwe observe a similar behavior: Sr, Rb, and Ba are more concentrated in soluble- and incompatible-element-rich mineral phases (Si, Al, and alkali-rich). Correlations between these trace elements and potassium in materials analyzed by ChemCam reveal a strong affinity with K-bearing phases such as feldspars, K-phyllosilicates, and potentially micas in igneous and sedimentary rocks. However, lithium is found in comparable abundances in alkali-rich and magnesium-rich Gale rocks. This very soluble element can be associated with both alkali and Mg-Fe phases such as pyroxene and feldspar. These observations of Li, Sr, Rb, and Ba mineralogical associations highlight their substitution with potassium and their incompatibility in magmatic melts.