INDUCED BREAKDOWN SPECTROSCOPY; DENSITY; GAS; TEMPERATURE; HYDROGEN; SPECTRA; LIBS

Laboratory plasmas inherently exhibit temperature and density gradients leading to complex investigations. We show that plasmas generated by laser ablation can constitute a robust exception to this. Supported by emission features not observed with other sources, we achieve plasmas of various compositions which are both uniform and in local thermodynamic equilibrium. These properties characterize an ideal radiation source opening multiple perspectives in plasma spectroscopy. The finding also constitutes a breakthrough in the analytical field as fast analyses of complex materials become possible.

Portable LIBS; Micro-invasive investigation; Pyrotechnological materials; Late bronze age workshop contexts; Tiryns-Greece;PIGMENT ANALYSIS; PAINTED PLASTER; COPPER; ABLATION; IRON; ENVIRONMENT; INSTRUMENT; ARTWORKS; BRONZES; GLASSES

Laser-Induced Breakdown Spectroscopy (LIBS) was used in the investigation of pyrotechnological materials (metal and ceramic items, glass-based objects, plaster-based materials) from several Late Bronze Age workshop and activity area contexts at Tiryns, Greece. The use of a portable instrument, which could be brought into the study place where all objects were housed, was crucial in order to establish the elemental content or verify the material composition of almost all materials analysed. In almost all cases, the LIBS analyses led to the preliminary identification of the materials investigated. In most cases, the results sufficed to confirm earlier research carried out or was in agreement with similar analyses published in the literature. The analyses demonstrate that the micro-invasive LIBS technique provides useful preliminary elemental characterization of most of the pyrotechnological materials while for some, additional work needs to be conducted for securing conclusive results. Essentially, the portability and compactness of the instrumentation enable its use in any workspace with a solid desk, light and electricity access which makes this technique very attractive for obtaining preliminary elementary results. While the technique remains limited by spot analyses it does open up an immense array of possibilities for routine characterization or speedy screening of different types of artefacts in any storage or museum context. These important methodological and scientific findings are considered prerequisite steps leading towards and aiding in responsible sampling strategies for further analyses. (C) 2017 Elsevier Ltd. All rights reserved.

Q-SWITCHED NDYAG; EMISSION ENHANCEMENT; OPTICAL-EMISSION; PLASMA; SPARK

In this study, we observed the evolution of the spectral emission intensity of a glass sample with the increase of sample temperature, laser energy, and delay time in femtosecond laser-induced breakdown spectroscopy (fs-LIBS). In the experiment, the sample was uniformly heated from 22 degrees C to 200 degrees C, the laser energy was changed from 0.3 mJ to 1.8 mJ, and the delay time was adjusted from 0.6 mu s to 3.0 mu s. The results indicated that increasing the sample temperature could enhance the emission intensity and reduce the limits of detection, which is attributed to the increase in the ablated mass and the plasma temperature. And the spectral intensity increases with the increase of the laser energy and the delay time, however, the spectral line intensity no longer increases when the laser pulse energy and delay time reach a certain value. This study will lead to a further improvement in the applications of fs-LIBS. Published by AIP Publishing.