Photoacoustic spectroscopy with light scattering samples.

Diffuse light scattering is shown, for some well-known examples such as powdered rare-earth oxides and semiconductors, to be a conditio sine qua non for obtaining any wavelength-dependent photoacoustic signal at all. However these photoacoustic spectra have not yet been used to get quantitative values of absorption coefficients obtained using well-known diffuse reflectance spectroscopy techniques. In view of these complications it is emphasized that photoacoustic spectroscopy should be concentrated on those applications which are unique for this method, such as depth profiling or special energy conversion such as photochemical oxygen production.