Multi photon excitation fluorescence imaging microscopy for the precise characterization of corrosion layers in silver-based artifacts

In this study, we present results of the implementation of multi photon excitation fluorescence (MPEF) imaging measurements to silver-based artifacts for the identification of the corrosion layers (generally composed by chlorargyrite, AgCl). We employ as an excitation source a compact femtosecond (fs) laser operating at 1028 nm. Silver-based reference alloys, artificially aged, were used as samples. Two and three dimensional images of the corrosion layers, detected in the reflection mode, are depicted. MPEF imaging technique was proved to be an ideal, diagnostic tool for the precise (axial resolution of similar to 1 mu m) thickness determination of silver chloride layers. Moreover, this technique has the potential to provide complementary information about the physical and chemical stability of silver-based artifacts, without affecting the art objects. The non-destructive nature of the MPEF modality, constitutes a certain advantage in comparison to the conventional techniques used for these kind of measurements.