The photoacoustic (PA) spectra were determined over the wavelength region of 1000-200 nm for polished and etched foils and powders of Cu, Ag, and Au. Aside from differences in signal strengths, problems with abnormal signal distortions due to reflection, and problems with surface oxidation in powdered Cu, the spectra were basically the same for the foils and powdered samples of the same metal. Analyses of the spectra showed that the PA signals were proportional to (1 - <i>R</i>), where <i>R</i> is the regular reflectance of the metal. Thus, the PA spectra were essentially reflectance loss spectra.
David Hodul and K. Douglas Carlson, "The Role of Reflectance in the Photoacoustic Spectra of Copper, Silver, and Gold," Appl. Spectrosc. 38, 159-161 (1984)