Thermal and optical characterization of pigments attached to cellulose substrates by means of a self-normalized photoacoustic technique

A self-normalized photoacoustic (PA) methodology, involving the front and transmission configurations in the Beer-Lambert model for light absorption, is implemented for the measurement of optical and thermal properties of thin layers of substances in solid phase. To achieve this, the corresponding theoretical equations describing the PA effect in the Rosencwaig-Gersho model, were used. This new methodology was applied for the measurement of the optical absorption coefficient (at 658 nm) and thermal diffusivity of paper samples with different colors. This last physical property was also measured for all paper samples by using a self-normalized PA technique, already reported in the literature, involving the surface absorption model. In order to fulfill the theoretical assumptions in this last case, the paper samples were painted, on both sides, with a black marker. The thermal diffusivity values obtained in both cases were quite consistent among themselves and with the corresponding ones reported for similar materials.