Analytical Sciences vol:17 Special Iss. SI pages:S398-S401
The determination of the water migration profile in starch is used as an experimental model system for the depth profiling of heat source distributions. A depth dependent water concentration, which has diffused into the sample during a timed exposure to a humid atmosphere, acts as a specific position dependent heat source. The direct and inverse relation between the water content and the frequency spectrum of a photothermal signal detected by a pyroelectric tranducer in contact with the sample is investigated. The inverse problem is treated by a neural network and a table lookup method. The profile reconstruction is illustrated for simulated and experimental cases.