Photothermal probe beam deflection measurement of thermal diffusivity of atmospheric air

A modified photothermal probe beam deflection system with a back pumping configuration is used for the measurements of the temperature-dependent thermal diffusivity of atmospheric air. The results are consistent and agree reasonably well with the literature values. The measured thermal diffusivity values are the same for the same measuring temperature regardless of the beam offsets and the deflecting surface temperatures. For the gas with known temperature-dependent thermal diffusivity, this method can be used to deduce the temperature of a gas from the measured thermal diffusivity value.