This is a major handicap in that shiny, smooth electrodes have much less surface area to accommodate reactions than irregular, folded electrode surfaces which, consequently, are higher performance. Rather than using reflected light, PDS relies on absorbed light. Through PDS, the absorption spectrum of the surface can be determined. This spectrum then allows scientists to identify surface layers of chemicals as thin as a single molecule. Experiments involving PDS are performed with electrochemical cells enclosed within transparent cases.
Monochromatic light is shone on the electrode surface at a succession of wavelengths.
Light at each wavelength is either absorbed or reflected by the surface, depending on the surface species' unique spectroscopic characteristics. When light is absorbed by the electrode surface, the absorbed energy is converted into heat. The more strongly the surface absorbs each particular wavelength of light, the more it heats up. As the electrode surface absorbs light and is heated, heat is conducted into the liquid electrolyte. Temperatures in the electrolyte drop as the distance from the electrode increases, forming what is called a temperature gradient.