Phase shift of photoacoustic signals from microparticles in liquids

Abstract
The wave equation in which the source term is coupled with the thermal energy migration was analyzed, and the physical meaning of the phase of photoacoustic signals generated in turbid solutions was clarified. These theoretical results, partially verified by experiments, showed the possibility for novel thermal characterizations and size measurement methods of microparticles. The theoretical limitation of the size measurement was 102 Å for samples with nonradiative relaxation times of 1 nsec.