MOLECULAR ISOTOPIC SPECTROMETRY; MASS-SPECTROMETRY; AB-INITIO; EMISSION-SPECTRA; ALO; AL2O; ABSORPTION; CHEMISTRY; SURFACE; SYSTEM

Identification of chemical intermediates and study of chemical reaction pathways and mechanisms in laser-induced plasmas are important for laser-ablated applications. Laser-induced breakdown spectroscopy (LIBS), as a promising spectroscopic technique, is efficient for elemental analyses but can only provide limited information about chemical products in laser-induced plasmas. In this work, time-resolved resonance fluorescence spectroscopy was studied as a promising tool for the study of chemical reactions in laser-induced plasmas. Resonance fluorescence excitation of diatomic aluminum monoxide (AlO) and triatomic dialuminum monoxide (Al2O) was used to identify these chemical intermediates. Time-resolved fluorescence spectra of AlO and Al2O were used to observe the temporal evolution in laser-induced Al plasmas and to study their formation in the Al-O-2 chemistry in air. (C) 2017 Optical Society of America

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

Laser-induced breakdown spectroscopy; Vector space model; Geological cutting; Identification;SAMPLES

Vector Space Model (VSM) was originally used in document retrieval. It is characterized by extracting the texts from the document and converting the document into a text vector space. VSM compares the similarity between document text vectors and text retrieval text vectors. The document retrieval is accomplished according to the similarity based on the nearest template principle of template matching in pattern recognition. This article applied such principle into the identification of samples based on the characteristic of LIES spectrum. To create the database of characteristic peaks of training dataset, we obtained the spectra template of all kinds of samples from the training dataset and extracted the wavelength and intensity of peaks from the spectra template. In another hand, to create the database of characteristic peak vectors for all the training samples, we calculated the spectral characteristic peak weight and converted the spectra to peak vector space. The characteristic peak vector of the test data set was obtained by the same way. The cosine value between the characteristic peak vector of test data and every characteristic peak vector in the database were calculated and the maximum cosine was taken as the identification result. Geological cuttings, the research subject, were identified by the VSM in this paper. The result demonstrated that the VSM could rapidly identify the spectra from 4 kinds of geological cuttings' LIES spectral and the correct identification rate was 100% after the spectra of the test dataset were averaged. The proposed LIES spectral identification method based on VSM can be expanded to the identification of other spectral data.

BULK AQUEOUS-SOLUTIONS; SINGLE-PULSE; ELEMENTAL ANALYSIS; OPTICAL-BREAKDOWN; OCEANIC PRESSURES; PLASMA FORMATION; WATER; LIQUIDS; NANOSECOND; PARAMETERS

Axial focusing arrangement effects on collinear dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) in a bulk solution were investigated by spectra and fast images. By properly defocusing the second laser pulse beyond the first laser formed bubble (LFB), brighter and larger plasmas could be produced due to higher breakdown efficiency and higher expansion efficiency. It is attributed to a distinct mechanism of underwater DP-LIBS that the plasma mostly forms at the bubble-water interface and then expands into the gaseous LFB. The results show that optimization of the axial focusing arrangement in underwater collinear DP-LIBS enables significant emission enhancements with relatively low laser energies. Published by AIP Publishing.

seashell analysis; LIBS; graphite enriched process; Sr/Ca; shell growth;RAMAN-SPECTROSCOPY; CLASSIFICATION; PROFILES; RATIOS; GROWTH; SHELLS

Seashell has been applied as an indicator for ocean research and element analysis of the seashell is used to track biological or environmental evolution. In this work, laser-induced breakdown spectroscopy (LIBS) was applied for elementary analysis of an ezo scallop-shell, and a graphite enrichment method was used as the assistance. It was found that LIBS signal intensity of Ca fluctuated less than 5%, in spite of the sampling positions, and Sr/Ca was related to the shell growth. A similar variation was also found when using a direct LIBS analysis on the shell surface, and it might be more practicable to track shell growth by investigating Sr/Ca ratio with Sr ionic line at 421.6 nm. The obtained results prove that calcium (Ca) is qualified as an internal reference for shell analysis, and LIBS is a potential analytical method for seashell study.

SINGLE; INSTRUMENT; LIBS

This paper reports the development of a compact double-pulse laser system to enhance laser induced breakdown spectroscopy (LIBS) for field applications. Pumped by high-power vertical-surface emitting lasers, the laser system that produces 16 ns pulse at 12 mJ/pulse with total weight less than 10 kg is developed. The inter-pulse delay can be adjusted from 0 mu s with 0.5 mu s increment. Several LIBS experiments were carried out on NIST standard aluminum alloy samples. Comparing with the single-pulse LIBS, up to 9 times enhancement in atomic emission line was achieved with continuum background emission reduced by 70%. This has led to up to 10 times improvement in the limit of detection. Signal stability was also improved by 128% indicating that a more robust and accurate LIBS measurement can be achieved using a compact double-pulse laser system. This paper presents a viable and field deployable laser tool to dramatically improve the sensitivity and applicability of LIBS for a wide array of applications. Published by AIP Publishing.