Orthogonal fs/ns double-pulse LIBS for copper-based-alloy analysis

The analytical response of a fs/ns double-pulse laser induced breakdown spectroscopy technique based on the orthogonal reheating induced by a ns-laser pulse on a fs-laser ablation plume is presented. All investigations have been performed in air at atmospheric pressure and employing certified copper-based-alloy targets. The emission intensities of the considered electronic transitions of Pb(I), Sn(I) and Zn(I) have been normalised with a Cu(I) emission line intensity belonging to the same considered spectral range. Emission data, acquired with inter-pulse steps of 2 mu s within the delay range of 1-200 mu s, have shown that fractionation takes place. Nevertheless, excellent linear regression coefficients (0.998-0.999), despite the target's large compositional variation and fractionation effects, have been obtained by integrating all emission intensity data along the whole inter-pulse delays used. Deviations from the theoretical ratio of the Zn(I)/Cu(I) emission intensities are shown and some hypotheses about the processes involved are formulated.