Femtosecond/Nanosecond dual-pulse orthogonal geometry plasma plume reheating for compositional analysis of ancient copper-based-alloy artworks

Plasma plume emission spectroscopy signals induced in air by 0.8 mJ of a femtosecond- Single Pulse (fs-SP) laser beam were enhanced by using an orthogonal geometry ns-reheating Dual Pulse (DP) configuration. The plasma plume temperatures of several copper-based-alloy standards and calibration curves of their Sn and Pb contents were conveyed. The resulting data showed an independence from the matrix composition so that, even for significant wt % variation of Sn and Pb, good linear regression coefficients could be obtained (0.99 for Sn and 0.98 for Pb). The DP configuration, here reported, using a low energy (0.8 mJ) of the fs ablating laser beam, was considered for determining the Sn and Pb elemental contents of ancient copper-based-alloy artwork fragments coming from the "Canne della Battaglia" archaeological site of Minervino Murge (Apulia - South of Italy). The results showed that, even by employing this low energy of the fs laser, which did not cause any visible damage of the ancient samples, the DP configuration supplied large enhancements and very well resolved emission lines of spectra providing information about the Sn and Pb contents which could support archaeologists work.