PHOTOTHERMAL DIELECTRIC EFFECT WITH LIQUID

A new photothermal technique for measuring the thermal characteristics of a liquid is proposed. This is based on the temperature characteris tic of the dielectric constant of Light-irradiated liquid. When an alt ernating temperature change occurs in a liquid material due to the abs orption of chopped Light, an alternating variation of capacitance is c aused due to the temperature characteristic of dielectric coefficient of the liquid and this variation is detectable with sufficient dynamic range and sensitivity using a frequency demodulation technique. Quant itative derivations are presented for the alternating capacitance vari ation in terms of the optical, thermal, dielectric and geometric param eters of the system. The experimental results for ethyl alcohol are sh own to be in good agreement with theoretical ones.