EXPERIMENTAL ASPECTS OF PHOTOTHERMAL RADIOMETRY

In photothermal radiometry (PTR), the thermal response of a given sample to time-varying illumination is detected via concomitant thermal radiation emanating from the irradiated region, to obtain spectral, structural, and other types of information about the sample. Excitation of the thermal response may be achieved in one of several different pulsing modes, with detection of the thermal reradiation over a wide range of wavelength bands, power levels, and frequencies. To fully exploit the power and versatility of PTR, it is necessary to choose judiciously the experimental conditions and equipment appropriate in each analytic situation. We discuss general physical spects of PTR, emphasizing fundamental principles and methodology related to the detection of thermal reradiation. PTR lends itself well to explicit numerical analysis, aiding the design and interpretation of experiments. Particular features relating to the investigation of high-temperture objects are discussed. A case study is presented on the analysis of thin films on metallic surfaces at ambient and at elevated temperatures.