Laser induced breakdown spectroscopy (LIBS) applied to stratigrafic elemental analysis and optical coherence tomography (OCT) to damage determination of cultural heritage Brazilian coins

• DOI: 10.1117/12.827724
• Publication Date: 2009-07-06T22:01:45Z
• Authors: Marcello M. Amaral; Marcus P. Raele; Anderson Z. de Fr...; Guilherme S. Zahn; Ricardo E. Samad; Nilson D. Vieira,...; Luiz V. G. Tarelho
• Keywords: Laser-induced breakdown spectroscopy

This work presents a compositional characterization of 1939's Thousand "Réis" and 1945's One "Cruzeiro" Brazilian coins, forged on aluminum bronze alloy. The coins were irradiated by Q-switched Nd:YAG laser with 4 ns pulse width energy 25mJ emitting at 1064nm reaching 3.10¹⁰Wcm^-2 (assured condition for stoichiometric ablation), forming plasma in small fraction the coin. Plasma emission was collected an optical fiber system connected to Echelle spectrometer. capability LIBS remove material exploited analyzed ablating layer from patina bulk. experimental conditions assure reproductivity determined evaluation three paramethers: ionization temperature using Saha-Boltzmann plot, excitation Boltzmann density plot Stark broadening. Calibration-Free technique applied both analytical determination elemental composition employed. In order confirm Edict Law results corroborated Neutron Activation Analysis (NAA). cases CF-LIBS agreed NAA determination. Besides major components alloy some other impurities observed. Finally, determine coin damage made laser, OCT (Optical Coherence Tomography) used. After tree pulses 54μg removed 120μm depth.