Elemental analysis of materials in an underwater archeological shipwreck using a novel remote laser-induced breakdown spectroscopy system

Abstract

LIBS analysis of submerged materials in an underwater archeological site has been performed for the first time. A fiber-optics-based remote instrument was designed for the recognition and identification of archeological assets in the wreck of the Bucentaure (Bay of Cadiz, South of Spain). The LIBS prototype featured both single-pulse (SP-LIBS) and multi-pulse excitation (MP-LIBS). The use of multi-pulse excitation allowed an increased laser beam energy (up to 95mJ) transmitted through the optical fiber. This excitation mode results in an improved performance of the equipment in terms of extended range of analysis (to a depth of 50m) and a broader variety of samples to be analyzed (i.e., rocks, marble, ceramics and concrete). Compared to single-pulse, an intensity enhancement factor of 15× was observed at the same irradiance value, 1.89GW/cm2. Thus, a longer pulse duration promotes the heating and melting of the sample, resulting in a greater mass ablated. As a consequence of the optimization of experimental conditions performed in laboratory, underwater characterization of ancient pottery was achieved.