Abstract

Consider the system shown in Fig. 1, where the sample is illuminated by pulsed, quasi-monochromatic radiation. Absorption of incident radiation causes surface temperature oscillations with amplitudes δT, which again modulate the total radiant excitance of the sample by amounts Here, σ = 5.67 · 10⁻¹²W cm⁻² K⁻⁴ is the Stefan-Boltzmann constant and ε ≦ 1 is the emissivity of the specimen, assumed to be an ideal greybody at absolute temperature T. Pulsewise sample irradiation thus gives rise to a component in the radiant excitance that varies at the pulse frequency, superimposed on the (generally much larger) CW radiant excitance M = εσT⁴. This constitutes the principle of photothermal radiometry (PTR).

© 1981 Optical Society of America